Nvidia's plan to provide PhysX support via driver updates has been coming to fruition, but it isn't without its snags. Recently, they have been accused of cheating in benchmarks when it comes to PhysX acceleration. Now, Nvidia has responded to those allegations by stating outright that they do not optimize "only for benchmarks" in any fashion.
This is not the first time such issues have come up, as both Nvidia and ATI have been accused of cheating on benchmarks in the past. Nvidia has stated that no software libraries or even a line of code has been changed in the benchmark whatsoever, only a runtime library which is updated during the benchmark install to allow the physics test to run on the GPU instead of the PPU or CPU. It's a decent read to see how Nvidia thinks and treats third-party benchmarks.
Nvidia acquired Ageia back in February, and since then has been looking for a way to capitalize on their investment with future GPUs.