There are at least 24 games that will be out supporting it sometime next year. Ten will be out by Christmas. How many DX 10.1 games will be out by the end of next year?
PhysX could prove very useful at elevated res or at a lower res in very demanding games. GPU PhysX more than tripled my FPS in Warmonger @ 1920x with all details maxed. I went from 20FPS to 63. That's a potential to be meaningful. That's moving from unplayable solidly into playable.
Warmonger at the tutorial start with all sliders to the right, or details maxed.
177.79 + PhysX 8.07.18 on the GTX 260 = 63FPS
As above but with an 8800GT doing PhysX for my 260 = 79FPS
177.41 no GPU PhysX = 20FPS