i know AMD/ATi and Nvidia are competitors but really they should both push Cuda as it directly competes with Intel and Havok.
Cuda is good but PhysX was a failure. People didnt want to buy a £200-£100 PPu they would rather buy a full on graphics card. Where as Cuda is just a driver and is free so people will be more inclined to try it out.
I dont mind using Cuda its not as if ATi have their own integrated physics processing drivers.