Surge Protection for the House

I've just received an offer from our regional utility provider (Sacramento Municipal Utilities District) for 'whole house protection', by which they install a surge protector on the electrical box for our duplex. It is free for three months, and then $6.95 thereafter, with only a 6-month total commitment. For $21, I might try it, but I wanted to get feedback first. If it makes no sense to do it, I want to know before having them install the protector and/or effecting the sound of our system in a negative way.
Thank you.