I sold my D90 and picked up a D300s yesterday. I mainly upgraded for two reasons; the increased AF performance, and the faster shutter speeds. Yes, believe it or not there were many times when shooting with my lenses wide open outside, that 1/4000 was not fast enough. I am thinking about exchanging it for the D700, but I might hold out and get a new lens instead. Anyway, I like it so far. The AF is way faster, and more accurate. I noticed that it focuses far better with my 50mm @ 1.4 then the D90 did.