i gotta say, the wheel is definatley worth it. For the first two days i was playing demo, i had just the mouse and keyboard. it was cool, but it got annoying, and you had no throttle and brake control.
The steering wheel definatley makes it alot easyer, and a LOT more fun, since the game is already pretty realistic.
But yeah, the wheel is worth every penny. The one i have, is for ps2, but since it goes through the USB port in the ps2, i figured i could use it through the USB on my computer too. It worked! Its the Gran Turismo 4 Logitech wheel, incase anyones wondering.