I'm afraid that will be (once again) a case where MS demos some cool (already working) feature, and then drops it from the final product.
Yes, I know it would be only eye candy, but then again, so is all the trasparency and shadows anyway!!!!
Some MS folks are saying that your gfx card should have 512MB of mem...I want to know why? None of the videos I've seen so far of Aero don't seem to need it or use the power of gpu to the fullest.