The Canon EOS M6 is the second in the latest-generation of the "M" series cameras.

Canon and Nikon have both "resisted" the mirrorless camera movement; Nikon is still sticking to their guns, but Canon (weakly) waded in with the original EOS M.  It wasn't very inspiring, to a large degree because it had to use contrast-detection autofocus, which is very slow.

The M3 went to a sort-of-hybrid system, and was somewhat better, with a higher-resolution sensor -- but lost a material amount of battery life.  But for tracking of any sort it was miserable, especially in other than bright light.

Neither of these were helped by the "kit" lens included (18-55mm), which was uninspiring.  A 22mm "pancake" f/2 lens showed up, however, and pretty-much made the argument for it as a "pocketable" camera with excellent image quality, as that lens was pretty darn good, and nicely-priced.  A lens adapter is available for $200 from Canon (MUCH cheaper for the third-party knock-offs) and since it's just a piece of metal with contacts (no electronics) there's little reason other than fit and finish to pay Canon's tax on that -- and using it allows you to run any of your existing EF-S or EF series lenses with full automation.

However, all the way through the M3 you were limited to contrast-detect autofocus with them, which while accurate was maddeningly slow and worse, in video mode "hunted" since the camera had no way to know which direction to move focus originally.

In the meantime competitors were and are out there.  Sony, with their 5000 and then 6000 series shooters and a whole host of micro 4/3rds cameras.  In reality the m4/3 cameras, other than the Olympus PEN series, are not really comparables -- they're heavier and a lot bigger.  The Sony's are true comparables.  But all of them suffer from "meh" lens quality (they all cheat bigly with "auto correction" for JPEG pictures) and very high, comparably-speaking, lens prices.  Remember that with any interchangeable lens camera the camera body is only a part of the investment -- lenses often cost more than the camera does!

The u4/3ds mostly have either hybrid autofocus systems or contrast detection, which is (again) accurate but very slow.  There are exceptions, but they're in the high end bodies.  Some of the exceptions, such as in some recent Panasonic u4/3rds cameras, are proprietary to their lenses which defeats one of the big reasons to buy into a standard platform (such as u4/3rds) in the first place.  True phase-detect autofocus is found in a few of these bodies, but not many, and the ones that do have it tend to be quite pricey.

Sony has PDAF, but you also get the (IMHO very nasty) Sony menu system.  Oh, and you get high lens prices too and a proprietary ("E") lens mount to go along with it.

On the video side, on the other hand, the competitors have won "bigly."  Nearly all of them will shoot 4k video in some fashion (although their competence and color depth varies a lot), where Canon does not.  Does this matter? It can, but be aware that none of these cameras have global shutter which means on a pan you're going to get a rolling-shutter or "jello" effect on anything vertical, and yes, it's very visible and there is exactly zero you can do about in editing later.  Many of these cameras are also extremely challenged when it comes to autofocus in video mode; in short, without true phase detect tracking or racking focus during video shooting with any sort of decency is very, very hard.  This doesn't matter much for "set up" shots where you would use manual focus anyway, but it sure does for casual use -- or any sort of impromptu video where you can't control the shot (think street video, newsy things, etc.)

Enter the EOS M5 and, now the M6.  The two are basically the same camera except that the M5 has a built-in electronic viewfinder and the M6 does not -- and is $200 cheaper.  There is a hot-shot clip-on available for the M6 if you want it, at (big shock) about $200.  For me the M5 made no sense, because the reason to buy one of these (either of them!) is for the tiny size with the excellent sensor, and the ability to use smaller and lighter lenses -- plus all my existing EF glass if I want to.  Further, since I wear glasses, I need some projection of the viewfinder from the back of the camera body or I can't see the full frame without mashing my glasses into the camera.  This is not a problem with my 5d3 but it sure looked like would be with the M5.  If I decide I need the viewfinder later I can add it, and it's a bit "higher" and thus should present less of a problem for eyeglass wearers.

As for Sony (which has the EVF included in the 6000 series) they're damn near impossible to use if you're left-eye dominant!  That's the price of having the EVF on the left far side of the body; you pretty much can't use it if you shoot with your left eye -- and I do.  Thus the Sony line was instantly eliminated from my consideration.

What's the attraction of this camera over a dSLR or one of the other mirrorless options?

First, the reason you buy one of these in the first place, in my opinion, for stills is that you want or need something small and light.  My 5d3, which is excellent, along with the 24-105L lens on it is a four-pound package and it's not small.  Yes, I've taken it hiking.  No, I didn't like it and there are plenty of times I'd like to have a small but really nicely performing camera.  This fits that bill well; it shoots as well as any of the other 24mp APS/C cameras because the sensor is in fact exactly the same.  It's also a quarter of the size and mass of my 5d3 with an appropriate piece of L-series glass on it.

So what else is on the "why this one" list?

A few things, in my opinion.

First, it has true phase-detect autofocus in the camera body on-sensor.  This means it will autofocus quickly and knows which way to move the lens in both still and video shooting whether using a native lens or an adapted one.  Having had the pleasure of PDAF on my dSLRs for a good long time I will not give it up for an inferior focusing system.  This instantly reduces the list of available mirrorless cameras to consider buying by far more than half.

Second, it's very small and light.  With a pancake lens it easily goes in a jacket (not jeans) pocket.  But even with the kit lens, which incidentally is newly redesigned and not bad at all and is an 18-45mm (~28-70mm equivalent) it's pretty darn small and light -- the whole rig weighs right around 1.2lbs with the strap, battery and memory card in it.  While the new kit lens does have some distortion and peripheral shading issues they're nowhere near what I've seen on other mirrorless lens cameras in terms of native performance, which means I can shoot in RAW -- which is a big, big plus as it retains all of the original dynamic range and information the sensor captures for later massaging.  The trade-off with the M-series zooms is that they are not wide-aperture lenses by any means and this does interfere with low-light performance.  Light, small and wide aperture are simply not three words that can be put in the same lens description when it comes to zooms -- it's a matter of physics.

So let's take a look at how it performs.

In short, pretty-much like any of Canon's better APS-C format cameras with the 24mp sensor -- which means the T6i and beyond.  Phase-detect on the sensor means it focuses quickly and accurately provided you have a reasonable amount of light.  It is not capable of quick autofocus in very low light conditions -- it reverts to contrast-detection in that situation, and can "hunt."  It behaves much like a T7i in "live view" mode, in short -- which is darn good.  It loses to a pentaprism/mirror dSLR -- any of them -- in the autofocus department, especially as light levels fall, so don't kid yourself in that regard but that's true for any mirrorless camera in my experience -- manufacturer claims notwithstanding.

The M6 also has greatly-improved buffer depth over the previous M3.  Shooting bursts is now something you can truly contemplate; it really wasn't before.  Between that and the autofocus limitations the M3 was never a camera I gave serious consideration to.  With that said this is not a sports camera and if you try to use it like one you're going to be disappointed.  There is some blackout on the screen when shooting bursts -- that's the price of an electronic screen instead of a pentaprism that simply lets light go to your eyes when the mirror is down.

Finally, the "face and object tracking" detection really works, including in movie mode -- with no hunting problems at all.  I'm extremely pleased with the capability there -- Canon has really stepped up the CPU power in these cameras and it shows.

The limitation in movie mode, incidentally, which will cause some people to say "no way" is the lack of 4k shooting.  The best you get is 1080 @ 60fps, which allows for a roughly 2:1 slow-motion effect.  I understand this is a turn-off for a lot of people but for me it simply isn't -- this for me is a camera that shoots excellent stills and very good video, not the other way around, and while 4k would be nice even on my fairly expensive and capable 4k HandyCam I often don't use that mode because of the rolling shutter issues and drop back to 1080.  (BTW the price of "getting rid of that" starts around $50k for a camera without this limitation, so no, it's not reasonable unless you're shooting professionally!)

The "newer" kit lens that comes with the M5 and M6 is surprisingly good.  I'm used to them being just one step away from literal trash and in fact contemplated the idea of sending the kit back and getting the body only plus whatever lenses I wanted if I thought this one sucked.  But I gotta say -- Canon has upped their game.  It's not a wide-aperture lens at all, so you need decent lighting, but that's the price of small and light - especially in a zoom.  On the other hand for still subjects the IS (stabilization) really does work -- just remember that it won't stop subject motion.  The corners are a bit soft but far better than the older version, and the center is quite-acceptably sharp.  The kit lens, in short, doesn't win awards but it produces very good images, it's small, light, and has a decent "up the middle" zoom range.  For about $110 over the price of the bare body it's a good deal and not a throw-away like most.  Allegedly the 11-22mm EF-M zoom is excellent (there are some people who have knocked its peripheral shading and accuse the camera but this is idiotic; if you look at some of the EF wide-angle zoom lenses you'll see what I mean) and I intend to check this one out for an ultra-wide -- it too is the same (physical) size!  The two lenses plus the body will come in materially under 2lbs which makes for a nice, light travel camera kit that scares nobody unlike a big fat professional-looking 5d3 with a big red-ringed lens on it and yet covers the ultra-wide to mild-telephoto (~17mm - ~70mm) range with a very usable set of glass.  If you want a mild wide-angle prime with a decently-wide aperture add the 22 pancake to the kit; it weighs nearly nothing and takes up almost no space -- but you got to bring another couple hundred bucks for it.

The other thing that's interesting is the integration of both WiFi and Bluetooth in this unit.  The latter is nice because you get a "free" remote shutter release!  The usual answer for that is one of the IR things, which I have, but being able to simply have your phone do it is a nice option.  I have had some issues with Canon's software, however -- it's finicky on my Android DTEK60, and works sometimes but not others.  Meh, but it's there.

I also like the plethora of dials and buttons essentially all of which can be reassigned, so I can set it up so it shoots almost-exactly like my much-bigger 5d3.  In particular I like "back-button" focus when shooting stills; it puts the "focus and lock" on a separate button from the shutter, which leaves exposure unlocked until the shutter is half-pressed.  This makes focus-and-recompose easy, but what's even nicer is that on the 6M you don't have to screw around to set a focus point -- the touchscreen is active just like on your cellphone.  Touch the point you want to focus on, hit the button and shoot -- no focus, hold, recompose and fire.  Nice.

The other interesting point is that in my brief use thus far object and face tracking (two separate modes) work quite well.  The camera is very good at keeping track of what's going on in the frame and following it.  It's not as good at tracking moving things as my 5d3 is, which can nail birds-in-flight on a high-speed burst repeated-frame basis but it also isn't a $3,000 camera.  It radically outperforms anything else I've seen in the mirrorless world with the possible exception of the Sony 6300 -- which gets pretty darn close if not exactly comparable.

The "Q" menu system is exactly what you expect on a Canon and makes quick adjustments easy off the touch screen.  It's arguably easier and faster than my 5d3 in that regard, which is really saying something.

The ability to use all of my existing EF lenses is a huge plus. I have several EF-series lenses and all have their purposes, from macro to wide-aperture portrait to sports and wildlife to starscapes.  The M6 autofocuses very fast (for single-shot use almost as fast as my 5d3!) on my EF lenses, with one exception -- I have a Tamron 150-600mm and it refuses to run in autofocus mode with that lens at all. This is almost-certainly a compatibility issue as it's not a Canon lens; it's fine manually focusing, but the lack of autofocus is somewhat of a bummer since that would give me a 1,000mm telephoto effective length and shooting at birds and such (anything moving, really) without autofocus is damn near impossible at that focal length.  My 70-200mm and other lenses, however, work flawlessly and fast.  The only "gotcha" is that the IS (image stabilizer) is engaged all the time when the camera is on, probably because of the PDAF on sensor and "continual" focus point selection.  I suspect this might have a material impact on battery life, but other than that it's a non-issue.

Update: I sent the Tamron in for a firmware update and it now operates perfectly on the M6....

The point of this exercise was to get something that I can comfortably add to my pack when hiking and not go nuts, while at the same time getting an effective "backup camera" for my big dSLR that can use my existing lens investment.  It's not waterproof (the 5d3 has a much-superior water resistance rating) but on the other hand no camera is really waterproof and thus I always wind up double-wrapping anyway when it might get wet.  It also will be a great addition to stuff in the car or just have with me -- I need to find a nice, small carrying pack that is just big enough to fit it and the second wide-angle zoom, at which point it could almost be a constant companion.  That will simply never happen with a full-size dSLR, and the best camera for any particular circumstance is always the one you have with you.

Finally, there's (thus far) a dearth of decent case options. No, I don't want a huge dSLR case.  Yes, I'd like something that would hold this with either the kit lens or the 11-22 on it and the other in a neoprene pouch.  I've not yet found the correct carrying case option in either a sling or "chest pack" style, but I suspect it's out there.

In any event this thing massively outshoots anything in a cellphone, ever, period, and it's as close to dSLR performance as I've found in something that's half the size, mass and really not much more expensive than the lower-end dSLRs in price. 

IMHO Canon has a big winner here when it comes to this market segment, either in this model or in the M5, provided you can deal with the lack of 4k video and want a small, lightweight and mirrorless setup.  While there certainly are more-capable cameras out there in the micro 4/3rds and other mirrorless formats you won't find them in this price bracket nor in this size-and-mass bracket either.  The only real competitor, IMHO, is the Sony 6300 -- if you like where the EVF is, you can deal with the menus and the price of additional Sony glass doesn't make you scream in horror (I'm not at all impressed with the 16-50mm kit lens they sell with those cameras and with the better lens available in a kit, the 16-70 which is a decent piece of glass albeit quite heavy you can almost buy two M6s kits!)

Pros:

• Small and lightweight; with a pancake lens will fit in a vest pocket
• Grip is comfortable while not being large; fits in the hand well compared against similar models
• Same sensor as other current Canon APS/C format cameras; exceptional image quality
• On-sensor PDAF autofocus is fast and accurate in reasonable lighting conditions
• Touch-zone focus works very well
• Face and object-tracking works exceptionally well in both still and video modes; no focus hunting
• Reassignable buttons and the Q-system (common to other Canon cameras) are retained
• Multiple dials and buttons can be reassigned and make adjustments easy
• Dedicated EV-compensation dial is nice (I like to ETTR about 1/3-2/3rd stop when shooting raw)
• Adaptable at low cost (third party adapter) to reasonable cost (Canon adapter) to any EF or EF-S series lens
• The kit lens is actually of decent quality, and the ultra-wide zoom is allegedly exceptional (and reasonably priced at $400)
• Starts up quickly, shoots fast and has decent buffer depth
• Micro tripod foot (but not a full-sized one) will allow battery door to be opened and is on lens center
• Value for dollar spent - the only rationally-comparable body (Sony a6300) wins on 4k and some water resistance which Canon does not have but loses somewhat on money with the (IMHO inferior) kit lens. If you upgrade the glass to a more-decent kit lens you lose big on both money and mass; that's an entirely different class of device IMHO.  Ditto for the GH4/5 series Micro4/3rds models and similar.

Cons:

• No water resistance
• Only shoots video at 1080p/60fps; no 4k
• Some third party EF-compatible lenses will not autofocus on the adapter (at all)
• ISO "auto range" behaves in a silly manner (I don't use it but some people might want to; maybe Canon will fix this with a firmware update)
• With the M6 an EVF (viewfinder) is an extra-cost option for the hotshoe (M5 includes at a small penalty in size)
• Not a large lens selection unless you use adapted EF-S or EF lenses and "M" series zoom lenses are narrow-aperture (which can interfere with low-light shooting performance)

Recommended.