Unifiying all videgame based physics under one engine is good. That's the point. It's ok having HAvok taxing CPU's, or having GPU physX (or PPU PhysX) but at the end of the day it's just more **** for you to buy to stay up to date. At least this way both major graphics cards vendors can include the same, better technology, and thus more developers will make use of it.
Nvidia and ATI would benefit greatly because as Physics get more demanding, it means you can sell more graphics cards for SLI/Crossfire.