+2  A: 

⌘-Z then redo

Ben Reeves
I always use that, not just in XCode. ( that missing symbol is the command-key, for the folks unfortunate enough not to be on a mac. )
Kris
Thanks Kris.I use "⌘-Z" and "Shift-⌘-Z" (redo) too, but it doesn't work if you move to another file, which is the main issue I think...Furthermore, I sometimes want to iterate through all recent edit points and I can't do that with undo/redo because of the side effect of losing the changes :(
Ori