Countdown
We have a laptop in the conference room that gets used for presentations and the morning Scrum meeting. Since the morning scrum meeting is typically the first use of the day, I get the joy of handling the aftermath of an automatic update. Here's a dialog I've gotten more than once:
Check it out - they warn you that it's going to be 5 minutes before restart and then have the sheer gall to ask if I want to restart now, but don't actually give me the ability to say 'no'. The button's there, but it's inactive.
I want to know what is so important that the restart is mandatory, but so minor that you're giving me 5 minutes to try to defuse the ticking time bomb? It boggles my mind.
Practical advice - if restart is mandatory, don't put a time limit on the shutdown. Either start closing applications (horrible), or ask the user to do so. Don't put me into a movie cliché, I have enough drama in my life already, thanks.