Often overlooked, the effect that the mains power that you use to power your amp, effects, etc. can have a massive effect on your sound, the stability & reliability of your gear, and the safety of it! This device removes electromagnetic and radio interference, provides a consistent voltage, and prevents spikes, etc. from harming your gear. Anyone who uses a valve amp as the basis of their sound will appreciate that consistent voltage plays a huge part in how the valves work, guaranteeing you sound the same night after night, in venues that often have bad and dirty mains supplies.
My band rehearses in a studio near Clapham Junction, London, underneath the busiest train station in the UK, and the Furman cured all my power problems and significantly reduced the noise in my signal path..
It is well spec'd for the price, and has great US build quality. I would say that if you are serious about your music, and your sound, this is an essential part of your kit. For less money than an average stomp box, you, your sound engineer and your audience will be grateful for the Furman. Buy one!