I will say this...I believe nVidia will put on the gloves and come out swinging with NV40. Quite frankly, I've considered them as a "follower" (i.e., laggard) to ATI for going on 2 years now with both performance and visual quality.
If they're even considering trying to "evolve" past ATI INSTEAD of really "pushing the envelope", they'll "ride the pine" for another year (i.e., a lot of people will buy ATI again, or will switch from nVidia to ATI the next time around).
As for me...I'm ONLY even considering an nVidia based product (and an older generation at that...Ti4200 or Ti4800 SE) because they have the feature set I'm looking for a relatively low price (i.e., I'm looking for good game performance without AA/AF WHILE having vivo for ~$140.00 retail).
As strange as this sounds...ATI does not seem to have a product on the market that fits my need.
Just my opinion though.