Very nice game, extremely addictive.
The only other time I've played Mario Kart was on Nintendo 64, and I was hooked then. A very nice detail on this game is courses from past games. The moment I saw the Moo Moo Farm I was right on it. There are so many courses and things to do, this game is just a blast.
Don't second guess buying this game, it may be going for a lot at the moment, but it's totally worth it. I've only had this game a day and I've gotten really far. Next stop is Wi Fi. ;]