I know what I don't want to see in GT6:
<a href="http://www.youtube.com/watch?v=ljGsF_Jgv_o">YouTube Link</a>
Forza 3 physics.
GT5 > Forza 3 & 4
Therefore, following the logic, let's avoid putting in curbs that can magically flip cars. Never in my life, have I ever seen a car ACTUALLY flip like that, since the 1960s.
Sorry for the sarcasm, BUT, we don't want to lose a race, because of some ridiculous physics flaw, in which all cars have the same body roll, be it a Lotus Elise or a Jay Leno Tank Car. In saying that, thank you, Polyphony Digital, for actually taking the time to consider body roll/chassis lean.
And then:
<a href="http://www.youtube.com/watch?v=PkZBuSmdCeA">YouTube Link</a>
More realistic stuff from Forza 3: people crashing, people flipping, and people skidding their tires in ridiculous ways.
<a href="http://www.youtube.com/watch?v=JF9Hu-VST58">YouTube Link</a>
And how to recover from flipping: turn the steering wheel, while the wheels aren't even touching the ground; the car will magically flip.
Nor do we want the AI from Forza:<a href="http://www.youtube.com/watch?v=HZQtLAHNs3I">YouTube Link</a>
"OMG someone spun? There's still 66% of the track left clear? That's not enough track; let's just stay here and wait. Yeah, that works. That'll make for good close racing. Yeah, we're going to win this race!"