I would like to second Troy's answer and note that JetBrains has AppCode in early access, so you can try it for free. It has the familiar UI of their other products, and yes, it supports vi! So far it has been very good. I have run into a few issues, and a few vi-isms that don't work quite right, but it is still better than suffering with Xcode. I do text editing with syntax completion in AppCode, but switch back to XCode to get into the GUI builder which is actually quite good in Xcode.
If you are an old vi-guy like myself, it is invaluable.