There is a lot riding on canon regaining top dog position, any flaws no matter how minor in another 1d camera would be devastating to consumer confidence and possibly lead to droves of defectors to nikon. It had crossed my mind more than a few times with the d3s.
Yeah, Canon knows that this is their last shot at this. This AF has to be perfect. The tens of thousands of 5D Mk III's in the wild with the same AF unit will quickly show any problems that they may be able to correct in the 1Dx.
So far, the AF looks to be the best unit on the market.