Are you prone to outages (Brownouts) or spikes in your area?
If not and you don't live where there is a lot of lightning, a mid price range device will be for you.
I know when to shut something off most of the time when there's a storm. It's common sense and where you have a problem is the unpredictable, I.e. Car into power pole, terrorism, etc.
If you have really expensive stuff, get a comparable Surge/Battery backup unit.