Not very: it fundamentally assumes you're making a game, so it draws 3D scenes and uses a continuous update loop, which taxes the battery on mobile devices. The

Not very: it fundamentally assumes you're making a game, so it draws 3D scenes and uses a continuous update loop, which taxes the battery on mobile devices. The UI tools are also just finicky enough to make non-game app development a pain. In addition, it does have a little size overhead - the smallest possible build on iOS (a blank screen) is 12 MB with all the optimizations on, and double that if you need to invoke System functions or libraries that need them.