I've also looked at mruby, but the language seemed quite complex. (It claims to have a Ruby compatible syntax, but also has its strange warts.) It doesn't help that its documentation is rather poor. Also by looking at the issues section I was pretty scared about the bugs that might come up while using this (https://github.com/mruby/mruby/issues). If there was any successful usage of it in game development I would have jumped in, but so far I haven't found any.