I suggest using the Wiimote + Nunchuck combo for Mario Kart, it works great (I can't get used to doing tricks and wheelies with the GC d-pad, it doesn't feel right.)
Also I play with remote only/Wii wheel sometimes... usually when the new competitions arrive every 15 days I will have a test run with the wheel, oh and I also use the wheel with local multiplayer, because I can pretty much thrash anyone I know in real life even using the wheel, I'd obliterate them if I used my usual remote+nunchuck.
Oh, and for Wii Boxing... just push through it, many people hate the boxing because they try it early on and it doesn't work for them, but if you practice you slowly start to understand how it works, and you can get all your punches to register and eventually aim them quite accurately.
