Nowdays, I don't run expensive electronics directly from the power mains.
A UPS is highly recommended, if only for the power line conditioning that comes with it. You may only lose power once or twice a year but, if the computer is running when you do have an outage, you will be glad that you had it, instead of cleaning-up corrupted files after a power loss.
In my area, we get at least 4 or 5 power sags per week, and those can cause some seriously odd symptoms, or an outright freeze, when they hit.
The UPS will at least hold-up the line voltage when you get sags, filter out transients, and give you time to gracefully shut down the system in the event of a full power cut.