It only lasted a little bit. I'd say two-to-five minutes. My desktop boxen powered down, but that's OK, I was wanting to reboot them anyway. The important thing isn't my desktop machines, but rather the instrument machines.
I work in a laboratory, and things have progressed that just about anything that could be done without the use of instruments and computers and analysis has been done sometime in the last few hundred years. Computers have enabled new ground to be broken, and there are lots of instruments that are connected to computers via USB or CAT5 or eHDMI cables.
One of these instruments has a UPS, or Uninterruptable Power Source, connected to it. Consider it a surge protector with 20 lbs of lead oxide battery connected to it. Thing is, the instrument uses the twist-to-lock power connector, and the UPS for that instrument only had the twist-to-lock UPS connectors. The computer connected to it did not have a twist-to-lock power cable, so it was disconnected from power.
Lesson: If you have an instrument on a UPS and the PC that controls it is not on a UPS, you do not have an instrument on a UPS.
We actually had an APC SmartUPS 1500 floating around the office, so I was able to close that barn door after the livestock escaped. Outages occur only once every four years or so here, so this is more threat than menace. But now I have a sense of what needs to be done.