These rubber skins fit snugly on your keyboard and have all the app-specific stuff printed right on. It’s questionable whether the things are that useful, although they most certainly are cool. After all, if you have already learned the shortcuts in Aperture or Photoshop that you use the most, you don’t need the skin. And if you haven’t learned them, then once you do, you don’t need the skin either! That said, they would be helpful for the learning process, and would also be very practical for marathon sessions or machines dedicated more or less to an app or two. And $30 isn’t that much to part with for what amounts to a pair of training wheels.