In my experience, the text-editor/command-line path is the only way to be truly "pixel perfect". Visual tools can get you most of the way there, but it seems you always inevitably have to touch the drawing code if you want true accuracy.
Oh, and as for Objective-C being a fast growing language? The rise of Objective-C is directly tied to the rise of the iOS platform. If iOS had been written in any other language, Objective-C would still be a mostly forgotten language today.
You can still use XCode's interface builder and use Storyboards and XIBs with RubyMotion. It's not as nicely coupled as it is with Objective-C, but again, RubyMotion is in its infancy and evolving rapidly.
Oh, and as for Objective-C being a fast growing language? The rise of Objective-C is directly tied to the rise of the iOS platform. If iOS had been written in any other language, Objective-C would still be a mostly forgotten language today.