@ Squilliam
I don't think so, the texture res improvements are expected considering the game uses 2 DL DVD instead of just 1 and will alledgedly require to install a DVD onto the harddrive (meaning many 360 users will need to upgrade with a relatively expensive harddrive).
I don't doubt Forza 3 will be much smoother than Forza 2 with regard to the curving, as to be honest some ingame Forza 2 screenshots look horribly curvy (especially back lights).
I think Gran Turismo 5 will come out on top with regard to overall graphics technology, but we'll have to wait and see until both games are available.