This game is a lot of fun, and despite being nearly 10 years old, it still holds up really well and plays great. Most of the game is fun and not frustrating (except for the second to last section of the entire game, right before the final boss; try not to punch your screen there ;) ). This may look like a kids game and may even be meant to be a kids game, but I think anyone of any age who enjoys gaming will have fun with this.
The only negatives are mainly due to its age: low resolution cut-scenes are ugly, yeah the graphics and character models are a bit blocky, the invisible walls you encounter don't seem to conform to the shape of the environment, etc. And that second to last bit of the final level just before the final boss will be an exercise in frustration and anger management. But really, none of these things are bad enough to be a dealbreaker in this game.
Worth getting at its usual price; absolute no-brainer when on sale. :)