This is more for ease of access, and I don't think it's meant to replace the controller. For when you're wanting to type something in without a keyboard, or you're sitting on the toilet and you really want to sign in for that multiplayer match.
When you have that extra buddy around and no controller for him. No problem, just use a supported phone. It serves a practical use. Good for maybe adjusting a music playlist while someone else is in game and there are not controller's available (could be charging one).
I know I am in the minority of users who doesn't like all of the "social" features being touted nowadays, but using your phone or tablet as a remote control to browse Netflix or Hulu Plus seems useful to me. I would never share a game clip but I would use this app.
I'm on a crusade against touch as game control! We don't need phones as controllers, we need controllers for the phones! It should be illegal to create action games that don't require a proper controller.