Nikon D800 test samples - dpreview

[Astro]

http://www.dpreview.com/news/2012/03/20/Nikon-D800-studio-test-samples

[tt]

Exactly how good the D800's image quality turns out to be is something that we're very keen to establish. On balance, increased pixel count generally counts as a good thing in everyday photography. The most important 'headline' benefits, all other things being equal, are that you get more detail in your images and greater scope for cropping. But there are potential downsides, too. The D3X, Nikon's current flagship, makes very high demands on lenses at 'only' 24MP and we wouldn't be surprised if some of the optics which D700 owners love so much don't shine quite so brightly at 100% on screen when bolted on front of a 36.3MP sensor...

70MB RAW files? Guess that eats up a few more memory cards (just like the 2x size change to capture the lens correction I'd imagine for Canon.

[Mt Spokane Photography]

Comparing the raw ISO 6400 images to the 5D MK II, the D800 looks close to the same, more noise in the white areas, but maybe a tiny bit more detail.  About the same story at higher ISO's. 
 
Thats not a bad thing, the camera is obviously intended for high amounts of detail at low ISO.
 
Maybe we will have some 5D MK III to compare soon.