I use a few of the Xcode 4 Fixins (https://github.com/davekeck/Xcode-4-Fixins), which despite their name are mostly compatible with Xcode 5. I use DisableAnimations, FindFix, InhibitTabNextPlaceholder, TabAcceptsCompletion, and UserScripts (which I wrote).
A bit of work was required when Xcode 5 came along but from minor version to minor version they haven't needed much in the way of maintenance.
I've been using XVim for over a year now and it's been reasonably stable. They have an issue with code folding but then I don't fold while the plugin is enabled.
Fwiw. Folding shouldn't (big shouldn't) crash it but navigation is not like vim is.(the cursor is hidden inside the fold while you do navigation stuff. It eventually moves out of the fold though. It's on my list of things to fix with xvim.
A bit of work was required when Xcode 5 came along but from minor version to minor version they haven't needed much in the way of maintenance.