With batman, they left an option in the settings menu for "optimized nv AA" This is just MSAA (an efficient method of smoothing jaggies) that both ati and nvidia can do. The issue was that if it detected an ati card, that option was not available. The result was the older standard method of smoothing jaggies (regular AA) that is much less efficient, became the method by which ati cards had to render AA in batman. That meant that Batman with AA enabled gave ati cards much worse framerates than Nvidia cards because the nv cards were using fast MSAA and the ati cards were using old ass slow regular AA. Same thing going on with NFS Shift.
For physx, Eidos and rocksteady took certain special effects of the game and packaged them to be able to render via Cuda on the nv gpus. These effects only work on geforce 8800 and higher (along with the MSAA). However, these effects (fog, smoke, sparks, particles shimmer, cloth, mattresses, destructible tiles, flying papers, aluminum cans, garbage, spiderwebs, destructible elements, haze, etc) can also all be rendered using an Ati card. They were just "removed" when cuda + nv is not detected since it is part of the cuda package. If you check rage3d, beyond3d or youtube you can see people with ATI cards + Corei7's running batman using MSAA and all the "physx" effects (because they edited the physx code, and tricked the game to thinking it had an nvidia card).
Nvidia would love to control the usage of these effects because it makes the game more emmersive and appealing to users of their own hardware, while decreasing the "coolness" of the game on ati hardware. The sad part is that if you know what you're doing, a few lines of code will have your ati card running perfect MSAA and your corei7 running all those fancy special effects in about 5 minutes, and probably at better framerates than nvidia (if you have a 5800 series). The really sad part is that, the more they do this, and get away with it, the farther apart technological competition becomes. The ati cards are already very powerful on the hardware level compared to G80/Gt200. With their talented engineers and hardware design team, it's bad that ati isn't as efficient with developer relations, driver model programming, and aggressive business practices.