I wouldn't recommend using a regular text editor and dealing with the iOS APIs. I pretty much despise IDEs, but sadly the objective-c paragraph long method signatures require it. That's actually why I didn't even bother with RubyMotion, it doesn't solve the thing I hate the most about objective-c.
I just use AppCode, with Xcode for interface builder and dealing with things like data models. It's closest enough to something that isn't a total piece of shit so that I can avoid slitting my wrists all day.
Having a text editor does not mean that completion does not work. ctags etc. provide such features. It might not be as good as completion using a static type checker and might have false positives, but "uninformed" completion goes a long way.
I just use AppCode, with Xcode for interface builder and dealing with things like data models. It's closest enough to something that isn't a total piece of shit so that I can avoid slitting my wrists all day.