They should had used a real physics engine like Havok. I've played 3 GPU accelerated PhysX games using my AGEIA PPU and the calculatios are crazy. Mirrors Edge was the only game with considerably less PhysX glitches and it would slow down for no apparent reason. The water in Cryostasis looks pathettic and stuff in the floor would move alone or jump around like if a Poltergeist event were ocurring in the room, creepy! In Batman AA, slowdowns would happen for no apparent reason, even if I stared to a wall touching my nose to it (Character's nose of course) it wouldnt go away.
Need for Speed shift isn't GPU/PPU accelerated but the most crazy things occured in that game, my GF was playing the game and she hit a car in the rear, and the car's vault door started to flip forward like a spinning wheel along with the bumper, and in the end of the game, all cars were doing the same, scary!!!