All:
I'm experiencing a complete disaster for the first time ever with a GM release of OS X. 10.11 is a continuning nightmare. I don't know why the GM is so bad when all the prior betas seem to be just fine.
1) The inital installation caused me to be unable to launch any applications. None. I've recovered from that using the usual profile recovery methods and inheriting the home folder, etc. However....
2) I'm now unable to log in to *ANY* iCloud services. I thought this was due to the poorly implemented 2-factor authentication Apple is using (it's highly unreliable when dealing with app specific passwords) so I turned it off. I'm still unable to access iCloud services including messages, facetime, etc.
Right now I'm thinking that my entire keychain has been hosed. The problems are so surreal I may never really be sure. Welcome to Windows 10 by Apple for the Mac!
DM