I'm an engineer but my emag and circuit theory is way too rusty to even begin to argue one way or the other on the technical details. I'm sure folks could use Maxwell's equations, Lenz and Faraday laws etc. up the ying-yang to prove there was or was not an effect to substantiate their arguments either way.
I do believe that there are factors, such as washing machines, rheostats, hair dryers, RF or whatever, that can add noise/distortion and corrupt the power that sits on the power line circuits of your house. Filtering/regeneration can absolutely improve upon the power being fed to your components in ways that are measurable and audible/visible. To me however, I find it tough to believe that the electricity that started it's journey far away at some power station somewhere, traveling through miles and miles of power lines, transformers, distribution stations etc., all manufactured by the lowest bidder, can be measurably improved in some way by a special cable in the last 4 feet before it enters a component.
But with as open a mind as I could have, I've listened to equipment with stock cables and listened to that same equipment with "upgraded" power cables. I can't honestly say I heard a difference much less an improvement.
In the end though, all the statistics and measuring and equations don't really matter. If you think you hear an improved sound from your system because of a power cord then good for you, they're gold. If you don't think you hear an improvement, power cables fall into the snake oil category. I don't hear an improvement from power cords so for me they are not worth it.
Just so you know, I'm not a fanatic who needs everything proven to him before accepting it. For example, I wear a copper bracelet on my wrist because I experience less joint pain in my fingers and wrists when I wear it. I haven't seen any credible scientific evidence to explain why that is, though I'm sure there are folks that will claim to be able to explain it to me. I'm equally sure that there are people out there that will claim to have scientific evidence to disprove the copper has any beneficial effect. To me it doesn't really matter whether it can be scientifically explained or is totally psychosomatic. I feel better when I wear it. For me the bracelet is worth it.
Same with cables. Some folks think they improve the sound, others do not. Your mileage may vary.