I have to add the obligatory pitch for just using RubyMotion. I use it/love it, and def recommend it for those that have become a bit annoyed with the verbose-ness of obj-c.
I love the idea of RM and would like to give it a try, but I keep hearing murmurs about memory management issues and other little glitches that crop up from time to time. I also hear that these kinds of problems get fixed very quickly, but the idea of being stuck even for a short time while waiting for a proprietary abstraction to be patched up makes me a bit hesitant to reach for it for a serious app. Are these concerns overblown?
I'm writing a RM app right now and believe these concerns to be overblown. They're overblown in the same way "Rails doesn't scale" is nonsense. The addition of WeakRef to RM helps significantly. And you just have to look out for gotchas.
There were some showstoppers with regards to memory leaks using procs/blocks. There's still a few major ones occasionally where you might be unable to use certain newer frameworks. You'll have to wait for them to fix it. But if you aren't on the bleeding edge, it's not so bad.
I believe there was an actual problem with Procs that they fixed a couple of months or so ago. The core developers seem to be active on Twitter, so you could ask the source directly if nobody here knows.