Looks like great competition for a $200 street 9800P, especially in shader-heavy titles. I'm not sure AA+AF performance will be as good, due to the much lesser bandwidth (6600GT: 1GHz equivalent vs. 9800P: 1.28GHz equivalent) and the NV4x architecture (math or texture access per clock, but not both).
But if it's $200MSRP, then its real competition is the 9600XT/X600XT, and it'll cream both of them.