Tip: you might want to put iPhone in "Airplane Mode" before upgrading.
(I got a call in the middle and had to start over... no biggie, though. Everything looks fine.)
((((( UPDATE ))))))
Do not put your phone in Airplane Mode when doing the update. The cell signal needs to be present in order to complete the process. If you did do this, just take your phone out of Airplane Mode when you're at the emergency screen, by attempting to place a call. It will tell you you're in Airplane Mode and ask if you want to disable - press disable button and your phone will then sync with iTunes. All is well.