IGN got their grubby hands all over Mario Kart Wii and had alot of interesting things to say about the game including their thoughts on the steering wheel controller pack-in:

we played Mario Kart Wii exclusively with the steering wheel peripheral exclusively during our short hands-on time with the game. This peripheral did, admittedly, have a large learning curve due to the fact that you have to learn where the “dead zones” are. Since the Wii Remote isn’t attached to anything but your hands, you’ll need to feel around where the center point is, as well as learn just how far you can rotate left and right before your kart stops turning. The only “force feedback” comes from the Wii Remote’s rumble, and admittedly the vibration isn’t muffled at all when in the steering wheel controller

I’m starting to think that given the choice I would probably use the Wavebird controller once again. They then discuss a few gameplay elements including the new way of boosting during a powerslide:

Mario Kart Wii changes things around a bit by not requiring players to rapidly steer in the opposite direction of a powerslide to generate the boost power. Instead, the boost power builds automatically during a successful powerslide, and the longer you hold it the more boost you’ll get out of it. As soon as you let go of the powerslide trigger (the button on the back of the steering wheel controller) your kart will jolt forward with a surge of energy. No more waggling the stick/control pad back and forth to generate boosts this time around.

Sounds cool. The part where they discuss the power-up’s is great also as they talk about a couple of new ones, even one that they didn’t get to see but was talked about.

We even saw the power-up that turns your player/kart into Bullet Bill from the Nintendo DS game that puts your kart on a high-energy auto-pilot. A new power-up popped up during our playtest: a POW block that will hover over your players’s head, and you’ll need to jump three times in a specific rhythm to get rid of it…or you’ll spin out.

Check the link for the whole writeup, it’s 4 pages long and full of great Mario Kart Wii information.