I'm surprised that DICE demonstrated Mirror's Edge on a PS3 rather than the 360 (I was not sure, but according to someone at the conference, they were using a PS3 on stage). These days, it seems very rare for any studio to give a presentation using the PS3 version. Of course, DICE has already worked on both platforms so it's not as if they need to learn one over the other. That must mean that the PS3 version is at least on par with the 360 version otherwise they would not have shown it (as you always want to leave the best impression).
The game looks rather stunning, though. I'm not sure about the storyline they're aiming for, but the gameplay and presenation is truly incredible looking.