A revolution in kart racing; with a few flaws.
You can customize everything, and you can create anything, but the load times to do this are comparable to gamecube.
That is all I am going to say about the load times, because I am not the kind of person that destroys something for what it doesn't have, I like to praise things for what it does have, and this game has a lot to offer.
There are 3 major game modes: Online, split-screen, and career mode.
Online game play is not one that I have experienced yet so I won't write about that, you'll have to go find a review written by someone who has experienced the online racing.
Split-Screen is one of the game modes that I have experienced; and it is one that I quite enjoy playing. The screen can be split into 4 mini screens, so you can play with up to four other people. Though I have not tried it (and I'm not even sure if it is possible) I have been told that you can play split-screen online. I'll have to try that out some time.
Career mode is alot of fun. You play through a relativley good story, and unlock customization options (car bodies, paint jobs, hair, clothing, hood ornaments etc), when you win the race, and you unlock even more when you finish the race's challenges. During career mode, there are tokens you can collect while racing. These tokens can be used in the store to unlock items. The token unlocking process is like a slot machine. You put in a token and hope to win something you don't already have. You only need to put in one token, but you can increase your chances of winning something by putting in two tokens, or five tokens.
The create mode is one of the most impressive features. You can create unique racers using skins, clothing, features etc, and you can create unique cars (though not all of the bodies are cars...) using unique bodies, paint jobs, equipment etc.
Track creation is very easy. All you need to do is drive around a steam roller while managing the height of the track. You can make very fun tracks in a matter of minutes. When you have laid the track you can either fill it full of traps and foliage (is that how you spell that word?) yourself, or you can hit "auto fill" and it will do a good job of filling your track.
Over all this game is very fun and a revolution in kart racing, and its only flaw (that I have experienced) is its load times, and those are relativley tolerable. The load times only last a minute at the most. Thirty seconds is the average load time (in my experience).