I have been interested for a long time in making filmic short videos.
Had my eye on the Canon 5Dmk2 for a long time, and when I finally had scraped up enough money to buy one, there were new choices available - The mk3 (out of my price range) and the announced 6D.
I waited until the 6D was available and then bought it, but I had some serious doubts based on some very mediocre reviews I had read.
There were some big complaints that the camera was not much of an upgrade over the 5dmk2 in terms of features and quality. That's partially true. But then again, I got this body new for about the same price as the 5dmk2 through a promotional credit card offer. The 5Dmk2 is now 5 years old. This camera may not be lightyears ahead of it's predecessor, but it IS an upgrade with a new cleaner sensor, a microphone jack, built in wifi & GPS, (which I have used for transferring photos when I couldn't find my sd card reader), and a handful of other small features that I believe all add up to make it a slightly superior camera than the 5dMk2 at a very similar price point. It was a no brainer to me.
I have also heard complaints that the camera chassis feels cheaper and is made with more plastic. I have felt other high end cameras like the 5dmk3 and the Nikon D600 and I will say is this does not at all feel cheap to me, plastic or not. The three cameras above feel fairly comparable. This is very solid, buttons and switches feel nice, and I don't feel overly nervous about breaking something on it.
I have also read that the weather sealing might not be as good on it. Not sure if this is true or not, but quite frankly I can't think of any piece of equipment this expensive that I would risk in inclement weather. If I need to shoot in the rain I'll get a protective case or wrap it in plastic of some sort.
Another huge complaint was about the auto focus system. The in depth tests I have seen seem to suggest that the auto focus holds it's own despite its minimalism. To be honest, I'm not sure I care one way or another. For video I'm going to be working in manual anyway, and for pictures if I want just a quick photo of something spontaneous I don't know that I'm going to be pulling out my two thousand dollar camera. If I pull this camera out, it's going to be because I care about getting a great or artistic shot -- and I'm going to be doing that manually.
Your mileage may vary. Perhaps if you are trying to film sports this would be more of a big deal.
Now to the very most important element - image quality.
I bought this camera with the intent of making short movies, but the still pictures have been so EASY that I've been spending an obscene amount of time just messing around. The images just look good. That is the best way I know how to describe this camera. I don't know much at all about photography and I can hardly take a bad photo.
Some people online have complained about moire and aliasing. I took one picture of some power lines that did exhibit some aliasing, but not enough to make the shot unusable. It really didn't bother me that much considering how great everything else looked and how seldom the problem cropped up in a noticeable way. Moire hasn't been much of a problem with anything I've shot either. Roofs and brick buildings have looked pretty good. Down the line I may consider a mosaic engineering filter to help with aliasing, but really it's not that big of a deal. I can work around it the few times it shows up, and the vast majority of the time I'm seeing beautiful images free of any noticeable artifacts.
Video looks incredible to me. These DSLR's can be shaky when you move handheld, but there are plenty of DIY plans online for cheap stabilizers, not to mention a good old tripod. I bought this camera for video and I feel that it delivers everything I expected from it, especially in this price range. I can't wait to get out and test it in more situations -- and to buy more accessories for it :P
One negative I have read online and completely agree with is a lack of headphone jack. How they left this one out boggles me. They did add audio metering so it's not impossible to get a feel for things, but really for anything serious I'm going to be purchasing a dedicated audio recorder.
I downloaded and am using the free Technicolor Cinestyle picture profile, and I find using it on both stills and video to produce a very pleasing, film like image. It's a much flatter picture style with in camera sharpening and contrast lowered, so to some it may appear soft, but it responds well to sharpening and other adjustments in post. To be honest I think part of the trouble with digital is that it's just TOO sharp. a little softness is kind of nice. Reminds me of an old Canon AE-1 my brother use to use. Additionally, most of my pictures were shot with the aperture wide open, so I imagine if I were to stop down the lens a bit it would be even less of a problem. I recommend downloading and installing this free picture style.
My second recommendation is that if you are interested in video like I am, or if you want to take great photos manually (no AF, etc) google M42 lenses and get yourself an M42 adapter. I have been using a couple old Takumar lenses and they just look beautiful - The build quality is extremely solid because they made things with metal instead of plastic back in the day. They are fully manual lenses so you will have an aperture ring in case you need to try to pull iris. And they are very affordable. I got an incredible 55mm takumar for around $50. I love it.
Download and install the firmware update from Canon's site before you shoot videos. There is a bug that prevents you from uploading videos to youtube. The new firmware fixes that.
Finally, keep an eye on the Magic Lantern project. I've read reports that the Canon 6D will be able to support ML and so it's only a matter of time before it will be available adding even more features to this already cool camera.
Bottom line, the camera just works and looks great. Sure, there are other options on the market that may be superior in some ways -- but they are also much more expensive and have their own quirks. If you can't take great photos or videos with this camera...you are doing something wrong.