Don't play, Don't play, Don't play.
Pros:
+ Well, it does get harder, but not much.
Cons:
- The Belly Sliding levels are very glitchy.
- The Dance level's top screen can be distracting.
- The music is distracting as well.
- It's just a bad game!
Let's start with the Belly Sliding levels, because they're the worst. The level design is dumb, with super-straight paths, very little jumps, and too many obstacles to avoid. Sometimes, when you go off a ramp and land, you flip over (which doesen't slow you down that much), or maybe you'll just flip over. The collectibles are very easy to get, and it's so darned stupid to shape speed boosts as fish with no eyes or fins. Finally, the finish looks weird, and in a blink of an eye, it will transform you to a stupid screen where the darned penguin just slides down a snow-covered hill.
If the dancing levels were more like Dance Dance Revolution (like the Wii version), the points this game earned would go up a notch, but they aren't, so the score went down a notch instead. Even when the circle is close enough for a good 100 points, the game occasionally just decides if it want to give out points or not. Also, I don't remember circle-shaped ice thing changing color when I stepped on them
So don't play it and save your well-earned money for Super Mario Galaxy.