rouss

Great write up, although not all the points are strictly speaking valid (epecially the one regarding future ios versions; since all the pre-release iOS firmwares are available for developers, there are chances RubyMotion will be updated in a timely fashion).

My take on this is the following: using RubyMotion, overhead will be tremedous - while debugging, you will need to make sure and double check that it's you who screwed things up and not RubyMotion's author(s). This alone is a major downside of the whole thing.

Hire a professional designer and spend your time programming. I personally don't think skill of "designing" can be learnt, it's something you already have, adjusting and refining all the way.