It doesn't seem to work as freely as the iOS 7 betas did.
I never registered my iPhone 5s since it was relatively new, and after installing iOS 8 to it, it wouldn't let me past the setup because the phone was not registered in the iOS Developer program.
Of course, I just logged into the developer portal and entered my UDID, restarted the phone, and it worked fine.
But all I'm saying is, if you don't have the luxury of doing that... Don't even try the update.
I never registered my iPhone 5s since it was relatively new, and after installing iOS 8 to it, it wouldn't let me past the setup because the phone was not registered in the iOS Developer program.
Of course, I just logged into the developer portal and entered my UDID, restarted the phone, and it worked fine.
But all I'm saying is, if you don't have the luxury of doing that... Don't even try the update.