nVidia has been pushing its Cuda enabled PhysX as the next big thing for a while now. For the most part the new PhysX effects have been less than stellar. That is until Mirror's Edge came along.
Mirror's Edge has some very impressive physics effects that bring a whole new dimension to the game. Sadly for ATi owners much of this is not available to you without a very high-end CPU (and then the code that offloads the Physics to the CPU is not very well done).
But the guys over at PCGamesHardware have found another way to get the Physics effect into the game without having to switch out your GPU. To do this they used an Old PCI Ageia PhysX card and an older version of the PhysX software.
With this combination they were able to get very good frame rates with an HD4870 running the game at 1680x1050.