The reason for DICE delaying the PC release of Mirror's Edge may be a little clearer.

DICE are retooling the PC version with enhanced graphics and - video card permitting - the NVIDIA PhysX engine to allow more accurate physics modelling of the virtual cityscape and the many, many things that can realistically fall off it.

I have to say, this is the first real compelling argument for PhysX I've seen to-date. I understand NVIDIA's been doing some impressive things with their recent drivers, too, although it remains to be seen if this is a fundamental shift across the board (probably not) or driver optimizations that ATI can mirror on their hardware (probably?) but no matter what, you gotta play both of these games. I can go into more detail... so I will. Articles pending, oh yeah.