Well allow me to elaborate - have you ever merged two nib files? With today's variant you merge XML. With yesterday's variant you simply don't do it because it'

Well allow me to elaborate - have you ever merged two nib files? With today's variant you merge XML. With yesterday's variant you simply don't do it because it's not possible. So you're merging an obtuse XML file at best. In my mind that's painful versus merging clean .h and .m files where we know what's going on. So he's using colorful language to describe such situations - A "nightmare".