I've almost wrapped two weeks of location shooting with a couple or 1Dx bodies (one from CPS, the other I rented at the last minute). I've shot around 800GB and I have to say, I really love the 1Dx. I didn't really expect to, but the files seem excellent (I'll know more after post-production), and the handling was excellent. The greatest kudos go to the autofocus. Wow, what a difference a few years make. I was shooting a lot of backlit, lifestyle action on a beach (for instance touch football in the water), and was blown away by the accuracy and percentages. It helped that I have the new 70-200/2.8 II, which seemed like it was designed and built for the 1Dx. I was concerned (perhaps foolishly) that the res would not be up to my 1Ds3, but the difference is very small indeed. Perhaps the best thing is shooting at ISO 100 to 640 and having virtually no difference in quality, was a huge boost.
I STILL would love a 36MP camera to compare with Nikon, but the 1Dx did truly replace both my 1D4 and 1Ds3. Anyone want to buy a 1D Mark IV......?