"Must Have" Option For Racing Games!
The Wii Wheel makes playing racing games (like "Mario Kart") much more enjoyable and easy to master. The Wheel feels very solid and provide a touch of realism that improves control.

The additional Wheels are not that expensive, so if you will be playing multi-player you should consider getting an additional one to keep the race "fair" :-)

Very highly recommended!

Helpful if you're used to a real vehicle
If you're used to driving a real gas burning vehicle, this will increase you enjoyment of WII driving games ten fold. If you've already mastered driving sims using the classic Nintendo controllers, you'll probably do fine without it.

I've only given 4 out of 5 starts for the overall rating because it's just a piece of plastic, molded like steering wheel. You could probably make something similar for less $ with an old frisbee or pie plate.

Gotta have it
If you have more than one Wii controller and more than one person playing Mario Kart, consider the Wii Wheel. While it is not an absolutely essential accessory for playing the game it will improve the gaming environment for all present. :) The Wii Wheel is not that expensive and it will eliminate the fuss over which child gets to play with a real steering wheel. I find I cannot get used to steering with a rectangular block held in my hands, it's just not natural!

More fun with 2 wheels
Got this extra wheel so we could race each other and it turned out to be a good decision. Mario Kart is a blast, a must have if you own the Wii.

Learning Curve
I previously mastered Mario Kart:Double Dash for Gamecube and felt though Mario Kart:Wii would be just easy and fun. It's not easy. Drifting is more essential and the Wii wheel takes getting used to. It was really frustrating, but now I really enjoy the game. I especially enjoy the incorporation of 'classic' mario kart race tracks.