As it is coming round once again to the time when major OS X and iOS upgrades are due (iOS 9 out now, and OS X 10.11 El Capitan is coming at the end of the month -- watchOS 2 has been slightly delayed due to the last-minute discovery of a showstopper bug), it seems like a good time to review tips on how to smoothly transition from one version of an Apple OS to the next without undue pain and gnashing of teeth.
