Product review (3 stars): Doesn't seem to harm, but doesn't seem to help
It may be that I'm using very hard well water with a lot of dissolved solids in it, but I honestly can't tell that this stuff is doing anything. I've tried using it exactly as directed, not using it at all, or using 50% more. I still end up having to wash out the humidifier once every couple of weeks due to gunk building up in it. The water doesn't seem to evaporate any faster with or without it.

Maybe it's helping others, but I don't think it's helping me.