Distilled water usage, while a viable solution, is incredibly expensive. Since the best price I can find online is $1/gal at Sam's Club, using this humidifier could cost $2/day. So in one month, the water will cost more than the humidifier---FOR ONE ROOM!!!! Also, think about dragging 14 gallons of water home per week! At 8lbs/gallon, that's 112lbs/week. Well, at least you won't need a gym membership anymore, you've got the weightlifting and aerobics covered!Caveat Emptor.
I've had all types of humidifiers and have settled on this type of evaporative model as the best compromise. Ultrasonics work great, no filters, no noise, no bacteria, but you HAVE to use distilled water or put up with incredible amounts of white dust on everything, so much that it will collect on and visibly dim your TV screen in a week---I was stunned. Probably 10 times normal dust! So there's the $60/month per room!
Warm mists are basically fan powered Petri dishes and tend to over-humidify.
IMHO, I'd use this evaporative humidifier with tap water, use some type of water treatment/antibacterial solution and change filters religiously--$12-15/year---YMMV.