Last month I posted Setting XIB Deployment & Development Targets Correctly. The article explains Interface Builder version settings in each XIB file and recommends sane settings to keep busywork to a minimum.
During a Subversion merge operation from the iTimeZone 1.3.5 branch to the trunk, I just about started to cry looking at merging the one XIB file I had changed on the branch. It was hundreds of lines of conflicts and not much had really changed. Why was their such a conflict?
Turns out that changing Deployment Target and Development Target in a XIB file dramatically restructures the XML. The large number of conflicts I was seeing, all gone once I had the inbound branch version of my XIB on the same version settings as the trunk.