White dust EVERYWHERE. Run this little gem for a week and then try to figure out why the TV looks so dim!!! Funny, but this happened to me. I live in a hard water area and I'm not going to feed this thing $1/gal distilled water(My one little evaporative humidifier does 2gal/day). So at $2/day and say 100days/yr use =$200? Yikes!
I'm a huge believer in humidifiers--my asthma and bronchitis were my motivation.
That being said, these ultasonics have some advantages---no filters to buy, no noise, steady output. Pricey, though. And dusty, like I said, it'll dim your TV it's so bad. Not worth $200/yr of distilled water, but still an annoyance.
My favorites are the evaporative style---they're cheaper, no dust, simple, use tap water and are effective---they won't over-humidify, they'll only go to about 40-45%, then they just can't "push" any more water into the air. So no wet windows.
Downsides---They are fan-driven, so they are noisier---I run them on High for the day, then Low at night in my bedroom and they cover up a lot of outside car noise that would otherwise wake me, so it's kind of a positive. You have to replace filters every year, so that's an expense, maybe $10/yr each. I use a water treatment that extends filter life--$3/yr for the whole houseful(3).
Hope this helps.