The PhysX SDK has been used in over 500 games - ranging from Gears Of War to Virtua Tennis 3. PhysX is pre-integrated into key game engines such as Unreal Engine 3 and Unity. A complete list can be found here.
On August 12, 2008, NVIDIA released drivers which enable PhysX acceleration for its GeForce 8xxx and 9xxx video cards. There have recently been hacks that allow users with both a Nvidia graphics card and a ATI graphics card to run a game with GPU acceleration, where the Nvidia GPU is used for physics, and the ATI GPU is used for graphics.
While PhysX is considered to be a hardware accelerated physics engine, only certain aspects of the engine actually are offloaded onto a GPU. These include;
There is a large misconception where many believe that the GPU takes on every feature of the engine. While this isn't true, time will tell for the future of what will be offloaded onto the GPU.
The major competitor to the PhysX SDK is the Havok SDK, which is used in more than 150 games, including major titles like Halo 3 and Uncharted 2. However, at this point in time Havok does not support hardware physics acceleration. Since Havok's take-over by Intel, AMD and Intel are now concentrating their respective efforts on Havok physics for their respective platforms.