They are XML now but they are so volatile that merging is still a pain in the ass.
With two caveats: - the classes section will sometimes be removed by IB. Ignore it - the last section, inferred something (priority? segues? metrics?) with 5-6 entries, can cause the storyboard to be unopenable. So, when merging, if there are changes to that section in both versions, just delete the contents of the section.