I use one with a big Panasonic Plasma and it does make a better picture...worth the money for that....if the current gets too high or low it shuts off and protects your gear...mine did that once...as for audio performance I didn't notice any improvement to the sound system I rigged up. A better device would be something like an Exact Power EP15A that does all the stuff the Monster does but keeps the current locked in at a steady voltage (my power fluctuates alot) and this will greatly extend the life of your equipment. So for the small amount the device costs I think it's worth it.
Larry
Larry