Follow-up: I upgraded 2 Macs to OS X 10.7.X using instructions from this site, then moved those, 2 iPhones and an iPad (all iOS 5.X) to iCloud without incident. The third Mac (OS X 10.6.8) iCal syncs correctly with the iCloud iCal, using workarounds also from this site. Have not attempted to sync Address Book yet on that computer, but expect that will work OK as well. Thanks to all who responded…. Ken - :-)