however, with some work and stuff (like limiting the distances it does parallax at) it could become pretty cheap (though, still more expensive than bump and normal mapping)
That looks quite impressive, had a bit of a run around in it, and it wasn't unacceptably slow.
The effect work quite well except near the edges of the screen, and can't do surface deformation yet - if you shoot the face, the bullet holes float on the wall's actual suface.