Currently using the remote/nunchuk combo. Tried the wheel first and just couldn't get used to it. I was sliding around over-steering all over the place, and I couldn't get the hang of drifting and firing with it either. Find the combo much easier to use.
Using Luigi at the moment too in the standard cart, although I haven't had the chance to unlock anything else. Spent all weekend playing it round my friends and so managed to unlock loads of stuff on his version as he's not too great at it. Now I have to do the same on mine!
Still haven't had too much time "in the driving seat" as it were so lots of improvement to be made!