However, Ageia hasn't sewn up the market. NVidia is also getting on the bandwagon by supporting Havok (as announced at GDC). Ageia claim that their card can generate more objects than a high-end graphics rig can cope with, so it will be interesting to see how a dedicated graphics card handles the task of physics too.
Microsoft is jumping in the fray as well -- not much is known about DirectPhysics, but if history repeats itself then a firm hand from Microsoft could do the hyperbolic world of physics accelerators a world of good. Ultimately, physics acceleration has a lot of potential, but the cost of an additional card is off-putting; as more emerges about the alternatives to PhysX, it'll be easier to make an informed decision.