Batman Arkham Asylum:

We tested Batman Arkham Asylum without PhysX effects due to the fact that Radeon cards don't feature PhysX. However, you can get PhysX support if you use a Geforce card alongside the Radeon. It's not something Nvidia had in mind, but it can be done.

You can check out HD 5870 results with PhysX effects, courtesy of a dedicated Geforce, here.