Well known wildlife photographer Andy Rouse is among the first (and selected few) to have had an EOS-1D X in his hands. This is more a kind of field-test, less a lab-setting based investigation of camera performance. Auto-focus is tested and described in a comprehensive way. Face detection is also put under stress, with an owl. While I suggest you have a look at the review on your own, i quote some excerpts from the conclusion:
The AF system I found to be astoundingly accurate [...] it could lock onto anything [...]. The images I have shown here are all razor sharp, again I was surprised to see so many in a sequence with such fast action. I’m quite happy to say that after my limited testing I can see that the AF system is probably the best I have ever used. Yes it is quite complex, but [...] for 99% of you they will be fine.
[...] noise performance. I have never seen a Canon file like it, at the kind of ISO’s I like to shoot at, the image quality is great, detail is intense and the noise is not an issue.