I think the biggest issue with GPU physx is the fact that the effects can be just as easily done on an open API like Bullet or Havok that is not dependent on a specific card e.g. Nvidia Cards only.
Name one Havok/Bullet game with SPH fluids as seen in Cryostasis or Crazy Machines 2.
Name one Havok/Bullet game with tearable cloth.
Name one Havok/Bullet game with fully dynamic smoke or steam.
These effects could be done on AMD GPUs. But CPUs will always struggle with them, which is why Havok and Bullet don't use them in games.
|Physx will still not perform as well as APIs like Bullet or Havok on CPU which were and are developed with CPU first in mind.|