No demos. Look to the new OXM for the Conker and Forza demos.
Actually, at the TRU I visited today in Mississauga, they had the Forza demo running. I tried it out, but not being a realistic racing type of guy, I wasn't particularly interested much in it.
The graphics are very, very nice. The screenshots I've seen of GT4 basically put it above Forza, though.
I don't think that the cars get damaged, as I ran the Ferrari 360 Modena into other vehicles and walls, and when I used the rear view, I didn't see any damage to the vehicle.
I can't really say much about the controls because, again, I'm not into realistic racers, but I think the car controlled well.
Sorry guys, I wish I could give some really detailed impressions for you, but I'm just not into these types of games. But the demo is making the rounds at stores now, so get down there and try it out if you can. Or pick up the new OXM.