InsideHW has published fine article about hardware PhysX acceleration, with some benchmarks included. Games (Batman Arkham Asylum, Darkest of Days and Mirror’s Edge) overview part isn’t much detailed, and only three GPUs were tested (GTS250, GTX260, GTX285), but this article is good read if you want to get in touch with current GPU PhysX posture.
Batman Arkham Asylum
Darkest of Days
You can read rest of the article here