This game is meant for multiplayer only. If you don't have anyone to play with, don't even consider touching this game.
The graphics are poor for the gamecube. They haven't changed it at all from the GBA. Even with some of the new things added, like the characters, they still had to make them look as poor as the rest of the game to make sure they fit in right, thus dragging down the overall quality of the graphics.
The sounds and music are good. The sounds match whatever activity you are doing, but are dull and redundant sometimes. The music is the same fast paced soundtrack you have on GBA. Nothing new or special.
The gameplay consists of playing simple mini games to achieve high scores. After a while this can get boring. Soon you and your friends will try and find something else to do. The mini games themselves are quite entertaining at first, but the fun factor tends to drain away each time you play.
This is a high score kind of game so the replay value is there, but the gameplay really will prevent you from playing this over and over again.
Whether you have lots of friends to play this with or not, there are certainly better multiplayer games out there. Eventually this game gets dull to the point where you won't play it anymore. This game makes a good rental, but not a worthwhile permanent purchase.