I shoot quite often at ISO 3200 and up on my D700 and have not that many problems. Your not going to get pin sharp images with digital noise creeping in at anything over ISO3200. I’ve printed dog agility images from Crufts this year up to 12×8 with no problems.
The D300 images are unuseable anything over ISO1000, they just blur and the loss of detail is massive.
Don’t know about the D3s but from what I have been told it’s allot better than the D700 at high ISO.