Overall this game is as great as you would expect for a Nintendo first party game. Awesome frame rate, graphics, the whole 9. The only thing I think that could be improved upon and thus knocked this from a 10 to a 9 for me is the online mode needs more options.
You can't change cars or tweak your racer in between races. You need to be able to have lobby's that you can browse and shop and choose from. For instance, when you sign up to play online you blindly get thrown into a room at 100cc (you won't know this unless you set up a custom race at 150cc and realize you were on a slower pace) and everyone just plays individual races until you decide to leave and that's it. If you were to set up a custom room with say, 150cc, Mushrooms only, Bikes only, etc, no one will ever join you unless they happen to have set up the same customized options. If there were lobbies you could choose from this would be different and you could join/leave at will.
Also, battle mode seemed kind of thrown together and there are no longer battle "arenas" specifically for battle you just battle on the track. It's "meh" but the rest of it is awesome. Just would like to see Nintendo do first party games with online functionality correctly for once is all. When my friends hop on and offline I should get a pop up like on XBL or something.
One last thing, in Nintendo's ongoing effort to protect kids from the scary internet and keep up the stereotype that they are a kids system you can only choose pre written PG texts to talk with in the lobby. It's pretty lame. I mean, no one should be raging at Mario Kart but still, I'd like to have the freedom to say what I want.
I can't remember Mario Kart being this much fun! They have locked characters that you have to win to unlock, and when you've unlocked the characters there are new karts to unlock, along with the kart upgrades like wheels and air gliders. Online is cool too, really tough players around the world. The graphics are great on tv and the wii pad. In fact the only thing I don't like about this game is that there aren't enough tracks. There are about 24 tracks if I'm not mistaken.
If you were a fan of the previous Mario Kart games this game will not disappoint!