From what I've seen ATi doesn't have raw power. That's 320 SP's grouped in clusters of 5, where only 1 unit does complex calc's. The SP comparison should be more like 64:128 (ATi:NV).
ATi will be faster if games are optimised for its architecture, while in general the 8800GTX should do better. I don't think we'll see "many" R600 optimised games, but the last statement is pure speculation.