Furman dominates the pro audio market AFAIK, and after getting their stuff and look back on audiophile company conditioners and really feel the latter offerings are mostly hype.
I have Furman's Power Factor Pro. At the electronics level, it reduces AC line noise, stores energy to provide high instant current, lowers power factor and provides surge protection. At the sonic level, it really reduces noise and makes treble smoother. I plugged a $40 Memorex DVD palyer from Target into it and got surprised by how close it sounds to my DAC1.
I once took the conditioner to my laboratory and plugged a $4k scientific instrument amplifer into it and saw its noise go down on the oscilloscope--amazing. This conditioner really works.