I never understand why in most damage models these days after the side of the car gets a hit the doors open... RBR had it too - was the first if I remember rightly.
Don't doors usually dent and cave in a bit? I'm certain I've never seen a car (rally or race) with a door open after contact... Although thinking about it, it happened in the BTCC once a couple of years back with Rob Collard, but my point is, doors don't fly open as often or as easily as these games suggest it does after damage!
Forza 3's tires behave like concrete. Extremely low slip angle threshold (you can especially see this manifested in the steering - you barely need to turn the wheel even in 900 degree mode). Weight transfer is also minimal, the cars have too much grip and corner too fast, and only the most powerful supercars will get loose if you just mat the gas at the apex. The game also drifts for you, even if you use a wheel.
It's a little bit different this close to Christmas, they had a slot to burn the 7 million (read this somewhere, dunno if its right) Blu-Rays, they missed that slot and obviously now it is almost impossible to do that so close to Xmas.