PhysX itself is a decent bit of middleware software - capable of advanced physics that are useful to future gaming titles... the way nVidia has handled it tho is not very positive or useful.
I think Mafia II may be the make or break game - even tho it doesn't use it as fully as I'd like - if it does enhance the experience significantly I think other developers will take note - if its a wet blanket then consumers and developers will continue to mostly ignore it.
+1