I don't generally recommend doing iOS updates on release day, but the betas have been out for a while (and nagging people aggressively!), so I'm less nervous. Do a backup and let 'er rip!
… Hours later … let 'er rip … download … ugh …
And then I come back to a white screen, saying "Attempting data recovery". FUCK. Dialog says "installing iOS" and stuck at 99% progress.
At present the screen's stuck, white with an Apple logo. Finally found HT201412 which has the extra-secret hard reset keys of Vol Up, Vol Down, hold Power.
And then I was able to log in and it's supposedly on iOS 12. But what's broken? Did it install completely? Who the fuck knows! SHIT. So now I'm restoring backup, because this is unsafe, and in maybe 2 hours when that's done, I'll try the update again. Did I say "FUCK"? Because FUCK!
So today's lesson is that nothing works, you should fear change, and never install anything until other victims have tried it. Also, backups are the most important thing ever, make sure you have them.