I just finished the campaign in this little gem, played through the music creation missions (which were really easy, but then again, I've been working with sequencers for over 15 years and know how to do this stuff) and created and published my own level. It's a short game, but it's cheap, solid and one purchase gives you both the PS3 and Vita version (with cloud sync for saves).
Unlike games like Little Bit Planet, the editor in Sound Shapes is actually pretty easy to learn and use. The biggest challenge, unless you're already familiar with music sequencers, is making the music for your levels. The community levels I've played so far haven't exactly been impressive, but my own experimentation with the editor shows that it's possible to do some very cool things with it if you're even slightly musically inclined.
The game is pretty straightforward. You control a little blob that sticks to certain surfaces. You're supposed to reach a specific target in the level, which requires you to go through multiple screens of challenges. On the way you pick up small coins, each of which adds one note or loop to the music playing in the background. As you pick up more coins, the music gets more complex and interesting. Enemies and other items in each screen may also participate in the music. A group of missiles may produce a groovy bass beat, for example, while a piece of text reading "aaaah" is actually a chorus singing that exact line. The only real rule to keep in mind while traversing the screens is that anything red will kill you. At the end of each level you're awarded points for each coin you picked up as well as the time you spent doing this, and are then placed on an online leaderboard for that particular level. Here's a video
of one of Beck's (yes, that Beck) levels from the game, with one of the best tunes as well.