HardOCP has written an editorial on AGEIA's PhysX PPU. They basically say the PhysX needs killer applications, otherwise chances are slim it will ever take off.
BUT, if you are a build-it-your-own-damn-self kind of guy, what is it going to take to get you to spend $250 on a PhysX card? I don’t know about you, but it is going to take more than some flying barrels full of eye candy to pry $250 out of my hand. The fact of the matter is that Ageia and their PhysX Processor is first at the mercy of the game developers, then at your mercy. There are some swanky games listed on the PhysX site, but do they really all utilize a $250 add-in card to its fullest potential, or at all?