They are pretty much on the mark.
FWIW the following are the known stats on the ZO6.
Engine size is 7.0 liters
500hp
475 ft.-lbs. of torque
275/35 18's at the front
325/30 19's at the rear
The wheels use a split spoke design virtually identical to that of the upcoming Ferrari F430. I do not believe they are runflats.
The interior is marginally different from the exterior with the difference largely in differently trimmed seats which now have the Z06 name in the seat backrest. Hard to tell more from the pictures I saw.
The exterior features the usual mesh grill but now adds wider fender flares and the obligatory fender badge. There is a hood scoop remarkably similar to that on the current SRT-10. Unconfirmed are reports of a dry-sump oiling system, carbon fiber body panels and more extensive use of magnesium.
I have pictures to back virtually all of this up but, regrettably, do not think it wise to post them. GM just had all the pictures pulled from every site that did so. I am disinclined to even e-mail them to anyone but, if you hurry, you may be able to find them on a few site that have not pulled them down yet. It will be a frontal shot of a yellow Z06 next to the C6-R. There is also an inside shot of the passenger seat and a terrific close up of the right front wheel showcasing huge drilled brakes.
See if this works for you guys but go quickly:
http://forums.corvetteforum.com/showthread.php?t=965875
I know many here like to pick on GM and the Corvette but I would like to think that we can all agree that with this car GM should do AMERICA proud.