Fun if you get past the game's big flaws...
First off, the voice acting is pretty sad. And some of the lines are pretty lame, too. (Honestly, how pathetic is, "Did ya bring your backpack? 'Cause you're about to get schooled!") The graphics aren't too hot, either, but I didn't mind that part as much since anything's better than stick figures. :P And the music and sound effects? They did practically nothing to help or emphasize the scenes' tones.
The storyline is what makes the game worth playing to me. It features five playable characters, all with their own deck civilization themes and personalities. The bad guys are pretty stereotypical, so there's nothing overly unique about them, but that is part of what makes the game entertaining. (And the arcade mode is an interesting twist on the game, too!)
Overall, I enjoy the game. Sure, it has its shortcomings, but its simple tone makes it quite fun. To sum it up: it's not one of those serious games; it's one of those light action games that you can play with a smile on your face even through the more "deep" portions of it. Just like the animated series, don't take it too seriously. Enjoy it and don't overanalyze.