My bet is on Kodak for the sensor.
1/250 strobe sync is not uncommon and that's what the rival Canon bodies do.
That hokey Nexus eyepiece costs $160 to replace! I wouldn't be too surprised if Nexus has considered doing this one. Who knows.
I'm with Herb on the pixel size. The 20D's results are impressive but the 1DMk2 does better with the same pixel count over a larger area. In the end, would you rather have 12MP at 5.5 microns or 22MP at 6.4 microns given the same process technology? There's some possibility we'll be looking at that choice soon. It's hard to do full frame or even 1.25 crop, but at the prices of these pro bodies our expectations should be high. The D2x sounds great, but will it be great enough to stand up to the 1Ds replacement that's certain to be coming soon? A full frame version of the 20D sensor would be quite compelling if Canon could deliver it.
I would be surprised if the D2x could actually outresolve the Kodak SLR/n or offer its dynamic range. The Kodak is realistically not even good to ISO 800 and in clearly an inferior body, but for underwater use the only things it lacks are fast strobe sync, really good autofocus, and a good viewfinder. If offered my choice between the two with identical housing support I'd take the full frame Kodak. Subject to change when we see the first test results, of course.