As promised here's an update after some time with my new BlackBerry DTEK60. You can read the original here.

Let's go down a bullet list and then we'll get into some specifics.  Buy this phone if:

• You are on either AT&T or T-Mobile, or any of their MVNOs (e.g. Straight Talk, etc.)  It is not compatible with Verizon or Sprint as it doesn't have a CDMA radio in it.  (One note on AT&T below.)
  
  
• You want a flagship-level device at a reasonable cost.  The phone benchmarks comparable to phones such as the Samsung S7 and is faster than anything in the previous class (pre-820-class CPUs.)  However, I caution people that "raw geeky stuff" rarely matters to actual overall performance -- although people do tout it frequently.  There are times that it really does matter (e.g. heavy-duty gaming), but they're rare for most users.
  
  
• You find RF performance to be extremely important.  This ought to be one of the primary criteria when it comes to picking a phone, but usually isn't for most people.  This device is clearly superior in that regard.  Even in the first couple of days it was obvious that I had a single-grabbing monster in my hands, and it has not disappointed since.  This phone's ability to get and hold a signal reminds me of my old Nokia 3390 -- it's that good.  There's an airport over here that shares runways with Eglin AFB and the road that goes past it is always a "dead spot."  Not only does the DTEK60 not lose the signal it doesn't lose LTE!  It gets close, but never falls back.  At my home where everything else I've owned drops back to HSPA+  (I'm in somewhat of a black hole) again the DTEK60 holds a functional LTE signal.  I do not know if the QFE2250 antenna tuner (which the Qualcomm 820 supports) is in there, but whatever they've done in the RF area it is wildly successful.  My Blackberry Passport was pretty impressive in this regard -- the DTEK60 is better.
  
  
• You want excellent cameras on both front and rear.  The Priv was known for an excellent rear camera and a crappy selfie cam, the latter forced by the slider and space considerations.  The DTEK60 has no such impediment; both are excellent.  Note that the main camera sensor itself is functionally identical to that in the Priv, and DXOMark rates both equally on a technical basis.  More on camera later; it's not the best available but it is excellent.
  
  
• The form-factor works for you.  Let's face it, form-factor (size, etc) is important.  This is not a small phone, but it's not a huge one either.  It's the same size as other 5.5" devices, basically, and some people will consider that to be too large.  I don't, but if you do then this is a factor to be considered.
  
  
• Security matters.  It ought to, and with the BlackBerry Android phones it is built-in.  DTEK tells you exactly what an app is doing and when, and gives you a quick and easy interface to shut off permissions if you find those actions objectionable and, if that winds up being insufficient, just uninstall the offenders.  As soon as you start looking at this you're going to find a lot of offenders and be either greatly restricting permissions or uninstalling things -- this comes from over a year's experience using the Priv.

I have no quarrels with build quality at all; it's just flat-out excellent, as is "in-hand" feel.  One point to be aware of if you run phones "uncased" is that the camera "bump" is there (as is the case with many devices) and that means running uncased is potentially hazardous not only to the glass back of the device itself (which is beautiful but since it's glass a sharp impact may shatter it) but also to the camera cover.  That cover, by the way, appears to be glass rather than plastic, which is great for optical clarity and scratch-resistance (important!) but makes it possible to damage it by impact.  I noted this is a phone you probably want in a case in my first look and I still feel that way, never mind the impact resistance a case gives you for the screen of the device.  Note that the Alcatel Idol 4s cases will fit this phone, should you want a wider selection than BlackBerry offers.  I am at present using an Incipio DualPro and like it a lot; it provides excellent protection (roughly "Otterbox" grade), keeps the "camera bump" slightly recessed and doesn't add too much bulk.  The case BlackBerry includes is functional as well, is a bit smaller in terms of its impact on device size and bulk but leaves the camera slightly protruding.

If you're wondering whether 4Gb of RAM matters here's your answer -- it does.

RAM matters more than raw CPU speed if RAM is constrained.  The difference between an app being cached (that is, already in RAM) .vs. having to re-activate it which involves reading it from storage, starting it and going through whatever initialization it requires is massive when it comes down to user-perceived performance.  3Gb devices are constrained by comparison to 4Gb ones -- it's that simple.  The counter-balance is that more RAM requires more power, and it requires it all the time since you must strobe RAM continually for it to retain its information.  We could wish that Android was more efficient with RAM use, but it is what it is as Android has always been a bloated mess from the outset and the reality is that with today's workloads and today's Android versions 4Gb is the sweet spot.  4Gb is also the limit for a 32-bit architecture and while today's processors tend to be 64-bit there is overhead involved in 64-bit operation that 32-bit doesn't have, so unless you need the capability the 32-bit system will actually be faster (even if only slightly), all other things being equal.

Now let's talk about the cameras since everyone and their brother seems to think this is arguably the most-important aspect of a phone these days.

There are multiple aspects to camera performance, and only some are captured by technical specifications.  DXOMark has tested the (main) camera and says its "equal" (in score) to the Priv, which had an excellent technical score.  I generally agree with this, but with that said let's talk about the differences, because there are some.

For background and to put some context on what follows I have been a photographer for pretty-much my entire life, starting as an early teenager.  I used to have my own darkroom back in the film days and have shot nearly everything, including cold-camera astrophotography for a few years when I had "at will" access to a very nice telescope setup in northern Michigan that cost far more than I've got available for such endeavors (and which at the time was so far beyond my personal means that it boggled my mind.)  Today I own a Canon 5d3 with a gaggle of lenses for various purposes and a very nice Sony 4k video rig, along with the usual plethora of tools to make use of those images (Adobe's suite, Vegas Video Pro, etc.)

The Priv's camera tended toward oversaturation of colors, which some people "like" but it is not what you actually saw when you looked at the scene.  It also had "ringing", probably related to that oversaturation, evident some of the time, and high-contrast edges often had minor artifacts that were visible in 100% crops.  Generally speaking performance was outstanding for a shooter on a phone, but I'm trying to pick some nits here.

The DTEK60 uses the same basic sensor as the Priv, however, it uses the entire 21mp frame instead of being limited to an 18mp one.  Why the limit on the Priv?  Simple: The Priv has OIS and a different lens system than the DTEK60, and both of those meant that illumination wasn't complete on the sensor, so only 18mp was used.  This means the DTEK60 has the same pixel size.  The lens on the Priv was f/2.2; on the DTEK60 it's claimed to be f2.0 but the embedded EXIM data claims f/2.2, so the DTEK60 either has a small (1/3rd of a stop) but real advantage in light gathering or is identical to the Priv, depending on which is correct.

The DTEK60 also does not exhibit the oversaturation that the Priv did.  I'm not sure why since the camera software (at the application level) is the same, but the firmware in the camera module is likely different.  Whatever the cause the oversaturation issue is gone.

Is the camera perfect?  No.

The large-mp-count sensor means that even with an f/2.2 lens under low light you're not going to get the same sort of performance you'll get from some of the cameras showing up in phones with 12mp.  There's a reason that Google, Apple and a few others went to smaller megapixel-count sensors -- it makes the pixels bigger, and thus the amount of light gathered per-pixel larger.  This in turn allows for a faster shutter speed for a given ISO, all other things being equal, which means less risk of motion blur and less sensor noise in low light conditions. Yes, you get less resolution but as with all things there are trade-offs, and some vendors have gone that direction.  BlackBerry did not. There is no free lunch, however, and in good lighting conditions resolution wins.  You choose; to get you must give.

The camera also does not have OIS, while the Priv did.  Does this matter?  Not as much as you might think, but under low light with a stationary object being photographed it can, quite materially, sharpen the image you obtain because it reduces (by a lot) camera shake.  Phones, of course, are hard to hold steady due to their shape.  This also matters during video shooting, but electronic stabilization can be used there, and the DTEK60 supports it.  The question to ask is how often do you shoot stationary objects in low light.  A person or group of people (or any scene containing people, animals and similar) is not stationary.  Neither is anything that can be impacted by wind or other movement sources. I can show you examples where the Priv outperformed the DTEK60 in this regard, allowing a slower shutter speed and a crisper image, but this actual scenario in real use is rare -- although darn easy to contrive for a test.  My personal view is that OIS is nice but not necessary and I consider it a minor, but real, ding to not have it.  It has not impacted my ability to take good shots at all.

The flash has less power than the Priv's by a small amount but it doesn't appear to impact the image quality.  Again, the issue is on the fringe of the range where you can use flash; the Priv will cover a modestly larger area than the DTEK60 in that regard.  I personally detest on-camera flash no matter the camera for the lighting field and effect it produces, but there are times you either use it or get no picture.  When the camera is pushed in low light but with a lot of dynamic range performance degrades in a reasonable fashion and while the defects are clearly visible with 100% crops you won't see them looking casually at the images.  Note that most uploads to social media or to blogs, including this one, are going to be cut down as the original files produced by the camera tend to be about 4Mb each so there's little point in trying to show you what the camera actually produces on a blog.  You simply need to either look yourself or find someone with the dedicated bandwidth resources for multiple huge files you can download and view at the 100% level.

BlackBerry's camera app has been updated a number of times since the Priv's first release and it is found on the DTEK60.  Beyond very simple exposure correction (which is nice) and touch-to-focus and take exposure lock (also nice) it allows for full manual exposure control should you wish.  Manual controls only work, obviously, when you have time to compose, set and shoot, but when you can use them the flexibility is appreciated.  Note that the one thing you cannot change in a cellphone camera is the f/stop and this means depth-of-field is not under user control; you must vary either shutter speed or ISO to change your exposure.  I like the BlackBerry camera app a lot and consider it a major plus compared against many others, especially the vanilla Android app that some phones have.  BlackBerry's camera app has face recognition and exposure compensation for detected faces (which can be turned off), and it works well.

Two things that are lacking on the DTEK60 camera, as with the other BlackBerry android handsets, are "Raw" capture and the Camera2 API.  RAW photos are huge and in addition worthless until post-processed, but they get all the data the sensor has and are how I prefer to shoot with my dSLR.  Having the option would be nice, and I'd like it a great deal if BlackBerry was to support it; since the DTEK60 has the ability to take a large SD card storage space is a non-factor.  Here's hoping BlackBerry adds this capability!  As for Camera2 the primary use for that is manual control and BlackBerry provides it, so that is IMHO far less important.

Here's an example of a 100% crop of a shot I took of the cat sitting on my lap in very low available light; there's very little artifacting, saturation is nearly bang-on as is white balance.  In short, that's exactly what the cat actually looks like when you see her with your eyes.  The problem with this shot at a 100% crop level is that the shutter speed and ISO combination made impossible completely stopping subject motion (if you think a cat is ever completely still forget about it!) and thus there's some evidence of motion blur when you dig into the image at the 100% crop level.

The shot, viewed as an image in Photoshop (or Microsoft's "photo viewer") in a "natural" size (e.g. fills my monitor) shows none of that defect; it appears to be very sharp and in-focus.  It's only when you dig in at a pixel-peeping level you see the cost of the larger pixel count in low light.  Of course as light level goes up that compromise disappears because shutter speed rises and ISO goes down; this shot has camera data in it saying exposure was 1/15th sec and ISO 757.

Noise (and moire!) is extremely bad at ISO 12000, but that's in the "ludicrous" range.  At ISO 3200 it's much better with the moire gone, and once you get down to and below 1600 noise is very good (and improves with further ISO reduction.)  That you can crank the ISO up far enough to make a photo possible in otherwise no-flash allowed conditions is interesting, but don't expect to like the results when you really push it.

There is a bug in the original firmware release; the positive exposure compensation adjustment is non-functional if the sensor gain is as far up as the software will allow, and the camera does not instead increase the ISO to allow the compensation to work.  All the other manual overrides work (including negative exposure comp.) This is something I'm sure BlackBerry will fix as they tend to be very "on the ball" with camera software updates.  In the meantime you can force the ISO higher manually and get your desired exposure compensation, so there is a workaround.

For video shooting the camera performs as expected.  It has electronic stabilization and can shoot in a number of modes and resolutions as shown here -- of note is that while it can capture at 4k slow-motion (60fps) only works up to 1080p.  You need a very fast SD card to be able to keep up with 4k recording -- UHS1/U3 (not U1!) is required and be prepared for utterly ridiculous file sizes!  If you run into trouble with 4k recording your card is too slow; there are a lot of cards that claim to meet spec but do not.  Stay with Sandisk or Samsung's Evo line and make sure they're U3 rated; you're going to pay more but they'll actually work.

Verdict: The camera acquits itself very well.  The "selfie cam" is excellent also, easily the best BlackBerry has ever put into a phone.  While "by the numbers" testing the main camera is equal to the Priv; in actual use it's a bit better.  Is it "best available", no -- not in low-light performance anyway.  It is suitable for a "flagship" level device?  You bet; color accuracy is excellent, the presence of artifacts (largely a function of the jpeg compression used) is very well-controlled and the stock camera app provides for full manual control if and when you desire it.

The screen is gorgeous.  As far as being accurate in its color rendition it's better than I expected.  AMOLED screens always have very deep blacks (since it actually turns off pixels entirely and has no backlight) but tend to lose in the color rendering accuracy department.  The common AMOLED sin of oversaturated colors and thus poor accuracy (although some people will claim that such inaccurate reproduction has more "pop" and thus they like it better) has been avoided on the DTEK60.  This screen is one of the best I've seen on a smartphone and it has the chops to be reasonably visible outdoors in direct sunlight which is where many AMOLED screens fall flat.

The fingerprint scanner is very fast and accurate.  But don't kid yourself -- fingerprint scanners are not very secure.  They beat nothing, and they probably beat a 4-digit pin, but they lose to anything more complex and maybe lose big.  If your fingerprint can be lifted from anything you've touched it can be trivially unlocked, so just keep that in mind.  With that said the boot password cannot be fingerprint (good) but I'd really like to be able to set the screen to not be able to be unlocked with a fingerprint but apps that can use fingerprints to remain available.  That would "stratify" the security model in the device since you have to unlock the screen first (the more-secure act) and then once that's done the fingerprint, while less-secure, is being used in the context of an already unlocked device.  Today there's no option to do that but BlackBerry could probably add it, and IMHO should.

The power amp (for headphones) is both nicely clean and plenty loud for nearly anyone.  The device sounds great through my Shure earbuds playing FLAC files.  Speaking of which, download the Onkyo HF player; I like it and it works exceptionally well.  If you're a real audio nut and want an external USB ADC there's a "pro" version of that player for a fee that supports them but that's not necessary for users that are happy with the built-in audio amplifier and headphone jack.

Notification sounds are a bit lower than I'm used to, even with the phone's volume set to maximum.  Phone ringtones start at a lower volume and ramp; I suspect there's an error here in that notification sounds are doing that too, but since they're short they end before the ramp happens.  If so that's something BlackBerry can easily fix in software, and I suspect they will.

On battery life it's simple: I'm impressed.  I've yet to run out of power in a day's use or need to recharge mid-day.  I've come home with 20% power remaining, but never a zero.  If you do need to "top off" this phone picks up power at an utterly ridiculous rate; about an hour from nearly empty to full with a QC3.0 charger.  The in-box QC2.0 charger will fill the battery from empty in about an hour and a half.  It appears BlackBerry and TCL got the balance of battery capacity .vs. power consumption right where it needs to be for a flagship in that most users and most workloads will get through a full day without having to recharge in the middle of it.

There are two things to keep in mind with regard to carriers.  First is the good -- T-Mobile appears to have no problem with the device including WiFi calling, Band 12 and VoLTE despite it not being listed as a "supported" device.  This is a big plus.  But AT&T appears to be blocking the phone's hotspot from working on purpose via their provisioning process when you insert an AT&T SIM (although the phone certainly can do it) and there are reports they have told customers that it's "corporate policy" not to allow it on devices they do not sell.  That's an apparent violation of the law, by the way, in that it implicates "tied sale" restrictions in anti-trust law, so if this matters to you then you should head over to the FCC web site and file a complaint.  We'll see how that turns out; I've done so, and the nice thing about the process is that the carrier has to respond.  I have in fact received a call from AT&T as a result of my complaint and read them the riot act; we'll see if that makes it way up the chain and leads to a resolution. Shaking the tree might just be enough, seeing as this "omission" could be an accident and with relatively-recent FCC action on unlocking codes and similar "that which is old but no longer defensible" sometimes is easily toppled over.  We'll see.  If Hotspot is not important then you don't care (and there is a workaround if you simply want to connect a laptop and it has bluetooth; since your account has Hotspot enabled it is not a TOS violation to use it either) but this sort of discriminatory conduct is something that should absolutely not be tolerated by anyone. Update: AT&T and/or BlackBerry have resolved this; the Hotspot now works on AT&T service.

What compromises are you making, other than the potential AT&T issue, by choosing this device?  A few.

• There is no wireless charging.  Is it convenient?  Yes.  Is it fast?  No, and what's worse is that it contributes to a lot of heating.  I had a wireless pad I rigged in my car phone-holder, but it would shut down if the AC wasn't blowing on the phone at the same time and I tried to use it with Navigation running, which materially reduced its usefulness.  During the summer this was a non-factor, of course, but in the winter the last thing you want blowing out of your vents is cold air!  Wireless charging's best use is at your home at night; drop it on, next morning you're good, and it saves wear on the USB socket.  The latter is less of a factor with USB Type C connectors, but the convenience issue is real.
  
  
• There are better low-light performing cameras out there.  However they're in phones that cost $200+ more; that's a 40% increase in price, and some of them don't have SD card slots either (e.g. the Google Pixel.)  I find the latter an utterly inexcusable and intentional omission designed to force you to buy a larger-storage phone (at much higher cost) or trust my data to the "cloud" (no thank you!) and thus refuse to buy a device without a card slot.  We're talking about differences at the margin however, not the difference between a "crap" camera and a "good" one.
  
  
• If you want to root the device and install some other ROM, forget it.  This sort of ability used to matter to me, and still does if I don't get timely updates.  But BlackBerry has promised to provide timely updates and has a history with the Priv of doing exactly that which stretches back more than a year.  They've also already delivered the November security update for the DTEK60, right on time.  Never mind that unless you're moderately (or better) skilled you're taking a fairly serious privacy risk in loading "third party" firmware on your mobile device.  If you never have anything you care about (like your bank app) on the phone then perhaps that's not important to you, but most people these days do conduct at least some of their financial transactions over a mobile device, and thus you should care about security and data integrity.
  
  
• If a multi-color LED is at the core of your "requirements" then this handset is excluded.  It has a red-only LED. I miss my multi-color notification LED. Is it enough to make the difference in what handset I choose?  No.

So we have four things that are "minuses" compared against some of the competition, but that's about it in terms of items I can identify.  There is certainly no difference in performance on a user-perceptible basis, you are giving up exactly nothing in terms of RF (in fact the radio performance is among the best I've ever experienced from any device), it's Android with all that's good (and bad) so you have the full Android app base and it has the BlackBerry "addons" that you can't get elsewhere, most-specifically DTEK.

Everything, in the end, has to be measured in terms of value received for price paid.  It is here that BlackBerry has really stepped out and upped their game.  Historically-speaking BlackBerry has tended to price their phones at the upper end of the range for a given set of specs, viewing their "special sauce" as having enough value to justify the ask.  This device is different; it comes to market at the top of the game but one notch in pricing above the mid-tier of devices.  This appears to be the result of BlackBerry exiting designing their own devices from the ground up, and instead selecting a reference design that already exists and asking for relatively-minor changes to be made to it.

The result of this change in strategy -- and pricing -- is that the only devices you can find with DTEK60 class specs at a cheaper price are the Chineesium devices with no promise of updates, an unknown provenance in terms of what might be in there you don't want (spyware, a root key that the Chinese government has, etc) and potential trouble with warranty replacement should the need arise.  Some of them (e.g. the OnePlus3) are disqualified for lack of an SD card slot as well.

Before you consider the "unknown provenance" comment to be speculative may I point out that it is definitely not.  There have already been devices caught in the last few months with "special" bootloader commands enabled from the factory but hidden that allow someone who is aware of them to break into the device.  This risk is real and if you buy something from a Chinese company with no accountability it's a risk that could bite you down the road.

The "mainstream" brands -- Samsung, HTC, LG, Google's Pixel, Apple and similar all have "flagship" class devices with comparable specs, and in some cases advantages (e.g. water resistance in the case of Samsung.)

The bad news is that all of them are much more expensive, starting at roughly 40% more than the DTEK60!

There's a hell of a difference in price between a phone that sells for $499 and one that sells for $699; you damn well ought to expect much better from the $699 phone, and quite-frankly there's no rational argument to be made on this point: You simply don't get it.

Instead what you get are improvements at the margin while having to fork up hideous additional cost.

For me, and I suspect for most others, the answer is and ought to be "no thanks."

If you hate money and will pay 40% more for a camera that can shoot better in very low light then buy a Pixel or S7.  If you tend to drop your phone in the toilet and hate money then buy the S7 since it's water-resistant (and 40% more expensive) while the other two competitors are not.

If neither of these descriptions fit you, signal-holding performance is very important, being able to easily monitor what apps are doing and control their behavior matters, a device that is inherently difficult to break into should you lose it or have it stolen is something you find to be of value, and you want a phone that runs with some of the best available today in terms of both specs and real-world performance, then buy the BlackBerry DTEK60.

The verdict is in and it is simple: Strongly recommended.