I'm experiencing this with the iPhone to iPhone transfer. Old phone said "complete", new phone said "12 minutes left" then rebooted itself. The progress bar has slowly filled up and I'm not sure if I should reboot it and go with an iCloud restore or just be patient...Mine has been sitting here on the Apple Logo and loading bar for a couple hours now. It's appears to be very very close to the end of the bar. It's not changing, and it's not getting hot either.