The major effect the PhysX card seems to add to games is how the weight of in-game objects, such as vehicle doors and tires, is altered. Somehow it feels as though these objects react a lot more stiffly when they are struck by bullets. However, the device does not prevent the clipping errors. Tires almost always partially disappear in the ground after grenades explode near them, regardless of whether the PhysX card is installed or not. On the whole, it does not feel as though the PhysX engine and the PhysX acceleration hardware are working in close harmony, yet.
You can read more at TomsHardware
Im certainly not getting on this bandwagon so early on.