Product review (5 stars): Work great.
I struggled with drum style furnace mounted humidifiers, trying to find replacement evaporative drum media (basically sponge) for models that were obsolete in a couple years, and always leaked as the shut-off mechanism never quite shut fully off.  Then after finding parts the motor would die.

Needless to say, I was looking for something else ... but limited choices as I have no basement drain. I installed a Aprilaire unit based upon recommendations of a friend in the business and it runs great, the media packs are reasonable, and readily available, and the thing doesn't leak.