Well Stereophile just reviewed 2 line conditioners; one was a very high-end Monster unit, AVS 2000, which cost ~$1500 I believe. Chip Stern found that it offered virtually no net benefit to the amplifier; it was actually detrimental and restraining in some ways. However, he did find that it improved the sound of digital source components nicely.
Now that is a high-end line conditioner which basically regenerates the power signal to some extent. It provided very subtle results overall. I would look at it as something to prolong the life of your components if you have really poor power (deviating significantly from 120 V).
So what do you expect for $100? It's a glorified surge protector and probably does nothing to solve moderate power fluctuations. Forget about sonic benefits. Nevertheless, I may buy one of those Monster units just to get a little more protection from a big power spike. I won't lose any sleep over any subtle degredation of sound quality.
-Cooper
