When I replaced my GTX 280 with this Radeon 5970 I actually had a slight drop in the performance of PhysX games, some games simply can't take advantage of these Crossfire cards.
Ultimately the games are still perfectly playable, no where near as bad as the performance I'm getting from DKS, the problem on my PC seems related to something else.
It's a shame, my excitement for the game is definitely waning after five days of fiddling around with hardware settings.
