First of all, let me acknowledge the elephant in the room. Yes, I now own a Canon DSLR. It's shocking, but true. I've railed against Canon in the past for a number of things--all true, by the way, but have eventually succumbed to the siren song of full-frame digital and my only two choices were Canon and Sony.
Past complaints of Canon DSLRs centered around three key factors: Grip shape, pasty images and tunnel-vision viewfinder. There are other nits to pick, but we'll leave it there for now.
The Canon 6D is the "Little Brother" to the Canon 5D Mk3 camera. There are a number of things removed, downgraded or otherwise hidden to not squelch sales of the 5D Mk3. The purpose of the 6D isn't to take sales away from the 5D Mk3, but to expand the base of users of full-frame by allowing crop-sensor users to move up without taking the huge financial plunge that the 5D mk3 requires.
While there are a number of missing features, the ones that are noticeably missing are the no dual slots. no CF slots, no PC Sync socket, lesser video capabilities/options, no headphone jack and no joystick. As long as none of these are show-stoppers for you, you do gain WiFi capability and GPS. The other trade-off is a plastic top to the camera instead of a full magnesium shell. While "ruggedness" might be SLIGHTLY compromised (doubtful), all you are really giving up is some weight and a greater likelihood of patina. None of these factors
were a problem for me.
When in quiet mode, this camera is very quiet. Olympus E-1 quiet. What a huge advance Canon has made in this regard. While there is a slight bit more shutter latency with quiet mode, the smoothness of the shutter is E-1 like.
Viewfinder. Not as good as the 5D Mk3, but very good. Canon changed the font of the displayed information in the viewfinder, which I find better for my eyes. YMMV. I don't get tunnel-vision with this viewfinder.
Shutter-release. Gone is the herky-jerky shutter release. Good riddance.
Grip. Several things have changed. The grip shape (with battery grip) is now roomy. My issue with my fingertips getting brutalized is nearly gone. This is a much more comfortable camera to hold and I do not get numbing as a result. Another factor is the light-weight. The 6D is significantly lighter than the 5D. There is enough of a thumb rest with "catch" that I don't have to squeeze the camera like I did with previous generations of Canon bodies. The 5D Mk3 is also much better. But the 6D has an advantage for me because of the weight.
Image quality. Well, 20mp is only slightly more than the 5mp of the E-1, so i wasn't really expecting too much. ;) The reality is that the pixel-density of both cameras is similar! It's just that the 6D has 4x the real-estate. The AA filter of the 6D is "friendly" and is easily
countered in the editing process. however, there is a noise-floor to the 6D images that isn't as "linear" as a CCD image. This is a camera that should use ETTR metering to avoid pulling up the shadows. As you increase the ISO, the noise floor creeps up from the shadows. Highlights don't change, but the shadows do. This is contrary to the E-1 which has a uniform noise characteristic across the entire spectrum. The creeping noise is more like the E-3, but with more dynamic range.
Image color. It ain't no E-1. HUGE difference. I can almost get the images to match, but it takes a massive amount of saturation and tonal twisting to accomplish. I haven't done any direct comparisons yet, but I'm certainly noticing the flatness to the images. I'll have to work on a profile for this camera.
Video capabilities. So far, so good. I've done my first shoot with it and am impressed. Magic Lantern does add some much desired capabilities that Canon didn't include with the camera. Sony still does video better, but I'm not complaining yet. I'm experimenting and learning what settings to use as the compression artifacts are a bit obvious at the one setting I used on Sunday.
WiFi capabilities. Already used them. Nice. The only complaint I have is that WiFi is not available at the same time as video.
Speaking of WiFi, do make sure that it is turned off when you direct-connect the camera to the computer for USB downloading of files. Otherwise, the computer won't recognize and transfer the images.
Overall impression. My overall impression is that Canon has done an amazing job with this camera and it is smartly equipped with features and capabilities that go far beyond "just a camera" and into a semi-automated tool for unusual applications. The previous owner of this camera used it for astrophotography and put 249,000 shutter actuations on it. That's right. This camera has a quarter of a million pictures run through it.
The only design faults that I can find with this camera would be the horrid little DOF button, the command wheel with directional pad in the middle (it's too small), the button placement of the magnifier, replay and Q button mean that you are pressing the wrong one in the dark. Other button and control issues are standard Canon interface issues. But I would like a one-touch WB button like I have with Olympus.
I have to work on the post-processing to get the colors I want out of this camera, but the dynamic range is EXCELLENT and the pixels do stand up pretty well to my level of punishment. High-ISO settings are amazing, but the dynamic range definitely does shrink as you climb that tree. The images stay clean, but there is no free ride.
There are other thoughts that I have on the camera, but some of those need fleshing out with the "Second Drive".
If there is anything about the 6D that I don't care for is that it's not quirky. It's a straight-forward, highly-perfected Canon camera that is predictable and reliable. Nothing really getting in your way. No surprises. It just is. It's the quirks that you fall in love with. No quirks means that it is as boring as a hammer.
How long I keep the camera is anybody's guess. It may be a matter of weeks, months or years.