I'm playing the demo on a 360 hooked up to a 32" Panny Viera, and graphically, the game looks absolutely stunning. I particularly like the scaling, and the fact that people/animals are shown as being tiny compared to the cities. So, for the first time ever (to my knowledge)there are no 60 foot tall humans cluttering up the screen!
As for any framerate/jerkiness problems; I haven't noticed any as yet, but this is the demo running from the hard-drive, and as such, will be optimized to perfection. Whether or not the full game running from the DVD is as smooth, remains to be seen!