yes it is, in particular faster the car is, higher is the advantage with a wheel and pedals.... just the precision and the fact that you can brake/accelerate at the same time are HUGE advantages....
I golded all nascars stuff with the ds3 but obviously the wheel is a huge advantage on any oval too...
I bought a wheel just for the X1 challenges (you can't gold these otherwise) and returned it few days later, cause i'm fine with the ds3 and golded everything else in the game but the wheel worth it... like i said in my first post, i'll buy one and keep it in a near future... i consider myself as one of the best GT5 player with a ds3, but i'll never be close from any online times i've seen so far, all done with a wheel...