As Ichiro said, PhysiX is owned by Nvidia, and Nvidia I believe already released support so that the 8800 series(and possibly 7800 series) can do additional Physics work like a seperate PhysX card would have done. Then there are plans for their future graphics cards to have this much more solidly implemented. That's why I choose PhysX, I think it will be around for a while, many big dev houses already used it, and probably most people already have this driver installed on their computer. If not, it's not hard install it on your computer, you don't need a Nvidia card or PhysX card to get the demos working either.