The two Pis that I used to replace 1) a firewall and 2) a fileserver, had their first real world test, yesterday.
National Grid, or whoever, decided that they would like to remove the power to our home at $SILLY_OCLOCK, yesterday.
Both boxes shutdown, once power had been removed. Once power was restored they came back up and carried on working as if nothing had happened! YAY!
Word to the wise, if you decided to use a Pi for something that you don't want to have to log into each time it reboots, to get things working again, bear in mind they have no realtime clock. There is a way around it, use fake-hwclock, which writes the time to a temp file, and reads it on boot up. This stops services like Squid crapping out when they see the clock suddenly jump forward 40+ years!