Folding isn't something a lot of people do. You can do it with any Nvidia card (so for example a 9800GT).
Nvidias problem right now is ATI are in the lead. Nvidia can try and overtake all they like (and probably will !) but ATI have been in a 4-5 month head start and lead dude.
I can absolutely bloody bet that they knew the 460 was coming and already have the counter attack fully in place. Why? because they should be more than ready. Even a simple price drop of the 5850 immediately gives them a better card for the same money. I also promise you that even though the 5 series were very reasonably priced ATI have been charging a premium for them before now because they had absolutely and utterly no competition AT ALL. They said jump, the paying customer asked how high.
Things are very very different now though