In the house I currently live in, I have seen voltage fluxuations from 80 to 170 (!) on a regular basis, making the addition of surge protectors vital to the survival of any electronic equipment, and the addition of conditioners necessary for audio equipment in order to avoid pops from the outlet. Before I moved here, I didn't take too much stock in conditioners, but seeing the difference before and after, in only keeping interference from my system, I am a believer.
But before I moved here, I also didn't have the pleasure of a +120V ground...