One of my biggest pet peeves is how the camera movement it closely tied to the car movement. It's more visible as the cars speed up. If you ever tried those mod utilities which made crazy hp monster cars, the replay speed seemed to speed up even when in normal mode as the movement was so "sharp".
I'd like to see inertia added to the camera and also so that it follows the aproximate car placement (i.e. a large box, so that small position changes don't reflect instantly on the viewpoint). I think GPL/NR2003 is still unbeaten in the replay quality department. You can slow the cars to a snail pace and still the replay stays smooth, can't do the same with LFS as 0.125x speed becomes a slideshow.