Product review (3 stars): It's hard to tell.
I bought this to use in my warm-air humidifier.  Even though I use it faithfully, I still have to use vinegar to soak the heating mechanism of the humidifier about every 5 days in order to get rid of the mineral build-up. However, who knows if it would be a lot worse if I wasn't using this product? I certainly can't complain about the price, so I imagine I will continue to use it.