Physx peaked quite quickly tbh. For me? it was amazing, and still is amazing, in Mirror's Edge. It really did add to the game. Mafia II was also very good with it as well.
Then it died. I mean yeah, it's now used quite a lot, but never to the degree it was then when people actually sat down and coded with it in mind. See the pattern? IMO Physx PPUs could have really changed the game, but they were expensive and needed exclusive coding, that was pretty much useless to anything else.
Then we also have to face facts that PC gaming is dying down again. Well, gaming in general is going through quite a large slump. Companies are going under, and those still around are just taking the pee. Like I said, £50 for a game I have to have spoiled because I can't enjoy the opening screens? do me a favour. I don't want to have to wait for the game to bloody start and then change the settings by pausing the action. That's really, spectacularly lazy.