The 1dx I had in my hands had some front/back focus issues, however, the canon support team is pretty quick , same day response and escalated to help the issue I had. My camera is on its way to the Canon USA factory to have it inspected and hopefully taken care of. I'm actually really impressed with the support response so far, looking forward to see how it all pans out! (I did use the AF micro adjustments to improve the situation)
Camera is solid, easy to use, mostly buttons in its settings. Tracking works well, but too short of time of use to really be conclusive. Resolution doesn't seem to lose a lot to the 5d mark III or II. It is heavy, and vertical grip isn't as comfortable as the horizontal, but not bad but could of been more ergonomic in design. Colors are great!
Silent mode isn't 5D mark III standards, which I really miss! 12fps upto 14 when you need it the difference in shutter. Tracking is my main concern. Just waiting for the return from the factory now.
Focusing in low light is better than the 5D mark III, since it can, but does it slower than good lighting, I don't need it to focus in pitch black which some Nikon owners claim, which is good but not necessary for me in any circumstances!
I'd love for canon to release a newer version of the Speedlite 270EX II, hopefully with more control, it's a flash given less praise than it deserves, something to compliment the 600Ex-RT In the line up!