the option for car damage in GT4 might be nice, but this is not the developers fault, licensing restrictions prohibit the cars from showing damage. Why this is not the case for some other games who knows. Maybe because they are not as realistic as the GT series, and nobody will take them seriously anyway?
Anyway, bottom line is who wants a damaged car anyway? That would be worse than tires that wear out in two laps.
The speed of GT play is just as it should be - realistic.
Online gaming is overrated.