Product review (5 stars): Air-O-Swiss humidifier cartridge is a great product.
I've used the humidifier for several years, and I love it.  In my small house, one on each floor is sufficient.  As the winter gets into the 20's and 30's, running this eliminates static sparks.  My dogs don't like being sparked.  neither do I.  I replace the cartridges each season, and I have nothing but good things to say about the whole unit.