IMO, power conditioners are definately *not* scams.

Everyone should have at least a basic surge suppressor. But the $12 kind you get at a hardware store use MOVs, and because MOVs are sacrificial in nature, when the MOV is gone usually you don't even know it. Here's the best I've found: www.brickwall.com .

Next level up is basic filtration. A la Monster, Adcom, Panamax, etc. Sometimes you get an improvement, sometimes not. But sometimes filters create more problems than they solve:

http://www.psaudio.com/articles/power_conditioners.asp

Next up, is balanced power. BP uses common mode noise rejection which is the exact same noise rejection mechanism used for balanced interconnects. The proof of the benefit of balanced interconnects has been known of for years, and now it's being applied to AC as well. Lots's of good reviews on power conditioners and balanced power units here:

http://www.hometheaterhifi.com/masterindex_power_conditioners.html

At the top of the heep, in my opinion, are the Power Plants by PS Audio. They basically take the AC from your wall, convert it to DC, and regenerate a pure AC sinusoidal signal. But they aren't cheap, and they are only about 50% power efficiant.

Me? I had an Adcom ACE 515 for years, the tried the 615 with and without some Richard Grey 400s's, then decided to read up on all this stuff, and finally went with an Equitech 2Q. One of the best purchases I ever made. Blacker blacks, more vibrant colors, no snow/noise/haze at all now for video, no effect on my system when the refrigerator compressor turns on, and there was a drastic drop in noise level for audio. But everyone has to decide for themselves how much they want to spend for what level of "conditioning". I think of it this way: a power conditioner does nothing less or more but let your system perform to its maximum potential, even in spite of poor quality AC.