Xiahou covered most of the salient features and advantages. I've been a happy APC-brand UPS user since the days of California's "rolling blackouts" 5-6 years ago.

One thing: once you've got your gear UPS protected, it's easy to forget about it, until a lightning strike nearby knocks out power. It is, in the end, a battery backup, and as such does lose it's ability to hold a charge eventually, just like a car battery. You'll need to replace it after about 3 years, in my experience (your mileage may differ); and checking its status on the switch to/from Daylight Saving Time, along with your smoke alarm batteries, is a good maintenance regimen.