I have a Monster HTS5000 who's biggest knock it that it whines if you turn up the blue gauge light too high. So I just turn it way down so you can barely see it.

Audio-wise I can't say that it does anything for crosstalk or separation of component interference, but I can't say it hurts either. When I wired my HT room, I ran 4 - 20A dedicated circuits to separate outlets for my HT. I give my RPTV and amps their own circuits and plug all of my digital equipment into the Monster HTS5000 and they sound fine. My noise floor is pretty low.

Admittedly, there are areas with real unstable AC power due to a number of reasons. I had a friend who said when his local transformer blew and was replaced, his whole audio system sounded better. I guess if you are in that situation, a high-end AC regenerator/stabilizer may be in order. Other than that, we all may be just paying lots of money for oversized surge protectors?