Nice game. Colorful tracks, tight and intense races and great gameplay.
Graphics:
The graphics were impressive for a launch title, and they still look very good nowadays. Some of the textures are quite ugly, but the tracks are very detailed and extremely colorful. Every location has it's own (quite cliché) theme; like the Arctic (with polar bears and penguins) or a harbor (with boats of course, and large container that can fall down). The water looks very nice, but the most impressive are the water and weather effects. The water spraying on the camera when you hit a wave looks terrific, as does the rain.
Sound:
Pretty solid. Nice rock songs, nothing special though. The sound effects are pretty nice, though the voice over can get a little irritating at times.
Gameplay:
This is the strongest part of the game. The game uses the GC controller perfectly, especially the rumble feature. You can actually feel the waves beneath you. The tracks change during the races, the waves get higher during storm or when something falls into the water. You even can build a wave behind you when you turn, and you can ride that wave to accelerate out of the corner more quickly. The gameplay is quite difficult to learn, but after a few hours, you'll get the hang of it. After that, you feel that the gameplay is very good and intense.
Lasting value:
It depends a bit on how much you like the game. The game is quite difficult, especially on the expert setting. You'll have to finish the expert championship to unlock the last track, so it's worth beating that. The stunt mode is pretty nice, but not that long. If you like the game and it's gameplay, you'll want to race the championships more often, and you can always try to beat your lap records ofcourse.