Well, I use Xcode because the performance loss in writing Objective-C without autocompletion is larger than the performance gain from using vim. However, navigation is just so painful, and "awful" is really being kind about Xcode's find/replace.
see:
quick lookup and a quick find as you type function. I like that if you press delete it will lookup the scope prior. so like if you type "addobj" and then delete a few times to "add" it will show you all the add commands again. Probably standard fare but not all implementations get this right.
Install was painless and I was able to map the invocation to ctrl-space, probably a better way to do it but I did it in a few seconds without looking anything up:
inoremap <c-space> <c-x><c-u>