It helped me, even though I have read that it would not over and over again.
Some clubs seem to have dirty power. Even my band room has this problem. I had issues with pops, buzzing, all kinds of strange artifacts coming from my bass rig. It did not ALWAYS happen, but it happened. I got the power conditioner, problem was solved.
Then, I plugged in our band room monitor power amp (a really old, beat up amp) into it and viola! The annoying buzz/hiss issues we had with that amp are gone.
there are guys on here who are well versed in these things, I don't count myself among them. All I can say is that, in my case, that sucker sure helped.
Got it on the cheap off ebay... just does its job.
Edit for price... I paid around $30