http://tomkarpik.com/articles/enabling-hardware-physics-acceleration-on-the-new-and-old-macbook-pro/ covers the full process required to tweak the drivers – not too scary, just adding a few lines to a file :)

Wonder if we’ll start to see more physics acceleration once OpenCL becomes more mainstream… if Havok (for example) could easily leverage OpenCL, it all might suddenly become more widespread.