I'm currently only interested in native code auto completion as good as in XCode where it understands the complete class hierachy and types half the boilerplate for you. For Storyboards or Xibs you'd still need XCode. I've long thought about a nice compiler from a simple text format to xib in order to have better version management capabilities, and it may be reasonable now with layout constraints to implement something like that, but I think storyboards would be best done in XCode.

I'll comment on this thread again once I've shared the objective-c emacs code.