As many other posters have noted, learning Obj-C is about 5% of the battle. Getting to grips with the APIs is the hard part and you have to learn them whether you decide to use Obj-C, RubyMotion or MonoTouch.
So if you think that Ruby is providing you with a significant shortcut here you're in for some disappointment.
So if you think that Ruby is providing you with a significant shortcut here you're in for some disappointment.