Great game, lots of fun. If you have a DS and do not have this game, shame on you (unless you hate racing games, which I think you can make an exception of for this one). Its fast, fun, and looks good while doing it.
It's Mario Kart. There's nothing really more to say unless you've never played it. Tracks are nice, not really any new items. And you're allowed to play the classic levels as well.
I don't understand how anyone can play this game if the difficulty was put higher than 50cc, the AI suddenly remember how to race a Go-Kart and completely blow you away from the beginning. How they achieve this, I haven't got a clue.