Seems like a hell of a lot of trouble just to write ios apps. I love Ruby as much as the next guy but sometimes you just have to invest some time into learning the native language rather than go through these elaborate and expensive workarounds
I knew neither Ruby nor Objective-C when I started (though I do know a few other languages, primarily JavaScript) and was able to begin legitimately understanding both within just a few days. I feel that, if needed, I could begin writing in pure Obj-C, though I don't think that that will ever be needed due to how seamless it is to integrate 3rd party Obj-C libraries into RM, as well as its Interface Builder support. Plus --and this is what I find most important -- writing in Ruby is just plain fun.
All in all, it was one of the most enjoyable development experiences of my life. Can't recommend RubyMotion highly enough.
Your mileage may vary. I'm a Ruby developer who picked up RubyMotion. I was up and running and productive with it within days, and after a month of part-time work my first app (which isn't extremely complicated but is by no means trivial) is nearly complete.
The relation cost-benefit seems pretty good. You are going to spend 500 USD per day to charge 150 USD per hour. Also, the quality of the instructors is something worth it.
