I really like it, I mean, this might be the best game in the series. It's a lot more balanced, where the really epic boxes definitly exists, but are a lot more rare. You can acually go through a grand prix withous having one blue shell, or lightning, being fired. This makes for a more skill-based game, like the first game on the SNES. Granted I have only ever played the console-games, so I don't know how the handheld games are, but I always heard they were better.
The most impressive thing about the game is the level-design. When I playd with some friends, the frase "that was a really cool track" was uttered very often. A lot of it has to do with the tracks often switching from air, ground and water, from normal gravity to upside down and all around. It feels great and plays great!