I'ld like to see rFactor incorporate Physx code, primarily to better model the shattering of carbon fiber and collisions with debris on the track.

But, there are other thing that could be modelled with Physx too. Like tire deformations, tire blowouts, refuelling hoses, rain spray, engine smoke, even those wisps of vapour trails that flow from the rear wing endplates on humid days.

AMD/ATi is suppose to be working on supporting Physx with upcoming cards. Though I'm not really sure how far along they are with implimenting Physx support.