Huge congrats on the app... with the iPad coming out, it's the perfect time for this.

A possible area for expansion (or maybe even a new app entirely). There's a whole world of classical music that is extremely competitive. Since you've got the iPad sitting on their piano, use the microphone to record yourself playing the song, and then it can be uploaded automatically and rated alongside others who've played the song.

Then you can have a leaderboard for each song, and even an overall leaderboard, like a global tennis rankings. They could challenge each other to a "duel" like a tennis match, or there could be a tournament. People can have their ranking, a profile, how old they are.

It would be hugely motivating to kids learning to play, and very disruptive/democratizing to the whole classical music world.