For me, the REPL is the key that makes this interesting. I don't really know much ruby, but I would consider picking it up again just for the interactivity you

For me, the REPL is the key that makes this interesting. I don't really know much ruby, but I would consider picking it up again just for the interactivity you get with a REPL tied to the app running in the simulator. This is a step in the right direction, a step toward getting immediate and interactive results when you code. The piece that I find a tiny bit lacking is disconnect between what you futz with in the REPL and what is your source. By that I mean, all the manual tinkering in the REPL isn't saved anywhere, you have to copy and paste. Emacs rectifies this sort of thing a little with swank and slime. Maybe there will be a mode for RubyMotion.