AFAIK, enhanced PhysX will run in both ATI and nVidia cards, Chris Taylor from nVidia said
this when they bought AGEIA:
Taylor was talking a lot about the principle of having a non-proprietary, free API, as opposed to an exclusive Nvidia physics API. Let's face it; this is what you'd need if you wanted game developers to take your API seriously over Intel's. 'The industry is crying out for a non-proprietary physics API, and there isn't one today,'
What has happened now is unofficial, I think it will be fully, officially supported in a future ATI driver release.
The problem is for nVidia, because Havok is property of Intel and only ATI will have hardware acceleration
for it, at least that's the situation today