The big thing for me (though there are others) is emulating old games. I realize this is probably not a super high demand use case, but I love playing NES and SNES games on my phone during... down time.
I was an iPhone user for some time, but got fed up with Apple telling me what software I could and could not run (without a jail break / side load.) I'd go back if they free up the app store market a bit. I don't find some of their restrictions reasonable.