First off, let me start by saying that this game is incredibly fun. It is a very, very vast improvement from the first game. The handling is better, the characters look (and sound) better, and the items (Although somewhat lack-luster) are much easier to use. The game is great fun to play with a friend (Or several via Xbox Live/Playstation Network/Steam etc), and it's even fun in solo mode. Compared to Mario Kart, the items are fairly boring and somewhat... Lacking. There aren't many and they have very few differences between them, leading to some pretty repetitive races. The 4Kids voice actors have been replaced with modern ones, taking away the annoying way they put emphasis on every single word.
-Fun as all hell to play, with or without friends
-Online and local multiplayer, up to 4 players locally
-Great character roster to choose from, though some questionable choices (Danika Patrick? Um...)
-Massive improvement from previous game
-New voice actors
-Items are few and too similar to each other
-Sometimes there can be a little too much going on at once, leading to some confusion
All in all, I'd say get this game, especially if you love racing games, or Mario Kart.
While it's not as good as Mario Kart, it is definitely a strong, enjoyable racing game, for everyone.