I wrote a somewhat more balanced review based on my experience with RubyMotion over the last few months (beta testing) http://merbist.com/2012/05/04/macruby-on-ios-rubymotion-revi...
What about MonoTouch? To be honest I think I'd look at that first if I wanted something other than Obj-C. At least I could take my non-UI code and run it on Android.