SpriteBuilder is a really nice tool. I started using it when it was still called CocosBuilder and I've used it for a game project [1] and had my own small fork with awful additions that were only relevant to the game I was working on.

I recently (as I started working on a new game) downloaded the newest release and I was really impressed. It is possible to quickly build rather complex UI scenes and game scenes.

I've actually just used it for a small iOS app side project, that only requires a minimal spartan UI and this way I can leverage Apportable [2] and easily release that app for Android, too. (hopefully, I'm not that far yet)

[1.1] https://www.youtube.com/watch?v=9J0mleRrcdQ

[1.2] https://itunes.apple.com/ca/app/flick-a-fruit/id771895296?mt...

[2] http://www.apportable.com/