I found that it was really hard to accelerate full throttle with the X button, I guess my controller's sort of worn out, I had to really hammer on it. I just switched R1 and X, and I like it that way now. Tap tap tap = traction controll.
Shift up and down are L1 and L2 respectively, everything else is just juggled around to accomodate that.
Has anyone ever driven one handed? IE; brake/accelerate and steering on one stick and the other controlls on the shoulder buttons and face buttons/d pad (depending on which hand).