I use an Equi-Tech Model 20 in my bedroom system. It is cool to the touch and does improve the sound in the areas that Charles1dad described. I upgraded to my current power filtration system (that can be seen on Audiogon listed in my systems http://cgim.audiogon.com/i/vs/s/f/1304179372.jpg
) that I use for my major Audio systems because of improved performance in all areas.
My current power filtration system (and Ive used it for at least seven years) consists of two Exntek Extreme Isolation Transformers (5 KVA each) that feed into my Audio sub-panel. The isolation transformers do run warm to the touch (96 degrees F and produce 55 dB of sound with the reading taken within one inch of the transformers). The noise and generated heat doesnt bother me because the power filtration system is located in the basement.
I hear greatly improved musical response in all areas with no major side effects other then the production of some hum, slight heat and of course any isolation transformer is going to consume additional electricity.
I think different brands of isolation transformers produce different results and most likely are somewhat system dependent. What works well for one audiophile might not produce the same results for another. The beauty of my power filtration system is I purchased the transformers used and did all of the labor myself. Total cost was well under $1000 and the results are excellent.