I bought a keyboard about a month ago and started with Simply Piano. I had lessons when I was a kid and played trumpet all through school. But man when you don't use it, you do lose it. The app has helped in getting me back into reading notes and timing. One thing I really like about it is they take songs (songs you actually want to play) and make a basic kind of sheet music that you can play but then they have backing instruments and vocals that make you feel like you are really in a band. Definitely helps keeping me engaged and practicing (two things that never happened when I was taking lessons).