I'm also waiting for the X. I work at a store were we sell them and everything else related. I had a serious go with the D4 today, we have one as a demo-cam. And I gotta say, IQ wise, not that impressed, noise is only slightly better than the mk4 at 1600 iso, but, and there is a big but, the AF is INCREDIBLE, the 1d X have a SERIOUS task to match it. It can't surpass it as I had a 100% hitrate with the D4 combined with the new 85mm. I shot bursts of a bike messenger 20 images shot @ 10fps and every single one was absolutely perfectly focused, and after using the 1d mk3 and 1d mk4 and now (in between) the 5d2 I can safely say that no Canon ever made comes even close to what the D4 did for me today. I had direct greenish (very bright) light directly into the lens and it locked focus like nothing. In very dark conditions (1/40s, f1,8 at 12800 iso) Continous focus locked, no hesitation AT ALL. I was blown away. And I didn't even adjust or fiddle with the AF, simply because that would require hours and hours due the useless menu-system, this is out of the box!
I seriously hope that the 1d X will outclass the mk4 completely (and I think it will) because the D4 AF is astonishing. It made the mk4 look like a toy.... Too bad the button layout and usabillity of the Nikons are suckier than suck....