As DirectX 9 cannot support a lot of objects it is definitely not the perfect answer for running physics on your GPU. TheInquirer spoke with several developers and learned that you will have to wait for DirectX 10 to see real GPU graphics out there. They learned that the DirectX 9 and the Open GL has a lot of latency for every physics and graphic operation. DirectX 10 solves this problem very aggressively as Vista and its Avalon graphics subsystem uses the 3D graphic engine to render both fonts and desktop in Vista or to do a graphic. DirectX 10 also adds the capability to implement a lot of independent objects in a scene and will let you add many details and small objects that will help scene realism. That's why the game developers want to stay away from GPU Physics as much as possible until it gets more mature. It is described as very complicated and it can easily trouble your gaming engine.