I tried RubyMotion before. Even published something to the App store. I liked the overall experience, compared to Objective-C you need a lot less code. But now that Swift is around - the benefit is not that great. Only that Ruby is a more beautiful and expressive language.
The downside is that you can’t use Swift libraries (at least when I tried it), but only Objective-C ones. And all cool new libraries are in Swift now.