I have mentioned before that I have several samples taken with the upcoming Nikon D800 camera. The TIFF files produced by the Nikon D800 are around 103 MB:

Unfortunately I cannot publish the entire images online but I can show you few JPG crops taken at different ISO settings. It's not much, but at least you can get some idea about the ISO performance. I already mentioned that with the D4 and D800 Nikon will make a clear separation in the target audience for those cameras. With its high resolution, the D800 will be for the landscape/studio photographers, where the D4 will have the speed and low light performance for photo journalists/sports shooters. This is a clear differentiation from the previous D3/D700 models that shared the same sensor/technology.

Here are five 100% crops taken at ISO 500, 1400, 3200, 6400 and Hi-1 (I do not have samples taken at other ISO settings). Keep in mind that those were probably taken with a pre-production D800 camera: