Here's a good article about the basic differences between Canon and Nikon DSLRs.
"One of the things that has a lot of people really bent is that the Nikon D3 can shoot at ISO 25,600. This is three full stops faster that ISO 3200, which for the record is three stops faster than ISO 400. (Just to put things in perspective).
"Some nay-sayers have commented, "Ya, so what. It's really noisy). As the teenagers say – "Duhhhh!". Of course it's noisy. It's freak'n ISO 25,600 for Pete's sake!
"As in the old joke about the talking dog, it isn't so much what it has to say but rather that it can talk at all. And at ISO 25,600 the D3 really has a lot to say."