Michael Reichmann of Luminous Landscape has posted a statement about the high ISO capabilities of the Nikon D3:

“So here, completely anecdotally at this point, is what I see, and keep in mind that I also own and shoot with a 1Ds MKIII, a 5D, and have shot hundreds of thousands of frames with all of the previous Canon pro cameras as well.
The Nikon D3 is a significant step up in high ISO image quality over any other camera from any other company. My guess is that it represents a real world improvement of at least 2 stops over anything I’ve yet worked with or seen.”