Lotta peeps don't seem to see PhysX as much of a big deal but I was pretty impressed by Batman....(I don't play many games but after seeing the demo, I had to try it). THG and Anandtech folks seem to think so too, but in the end only you can decide if it's worth the $65 to you. The 2nd link gives you a chance to see PhysX enabled / disabled side by side.
that would bring down performance of processing physx from the nvidia and then integrating it with the ATI
PhysX does not have much of a performance hit. Some Benchmarks I've seen show about 0-2% performance hit in FPS.
There is no integrating of physX processing, nor any integrating of it with an ATI gpu in it's use. PhysX is an API designed to do math on a GPU instead of the CPU, since the GPU is better equipped to do math. PhysX has nothing to do with rendering graphics, there are no integrating issues.