Very interesting article comparing RubyMotion and PhoneGap:
It’s the same feeling we get from Java desktop applications: write once, feel wrong everywhere
RubyMotion may be good, but I will continue coding in Objective-C, with Xcode for iOS. Just use the native tool of your platform and the native language and you will create the best experience for you app: Objective-C on iOS, Java on Android, C# on Windows Phone etc… Learning the language is not the difficult part, especially if you’re a developer. What’s difficult is learning the frameworks, and the convention of the platform. You will spend more time fighting with UIKit or CoreData than having issues with Objective-C and this will not change if you code your app in Ruby.