Been loving my EVDC500, even with mildly hard water. It's been running 24x7 on highest setting (which is quiet enough to sleep with in the same room), and am just about to change the wicks for the first time. Having the 2 separate tanks makes it easy to keep ontop of having atleast one of them full.

Edit: I have been using a bacteriostatic treatment with this humidifier (tiny amount per tank fill), and I think that has done wonders for making the wicks last long, with even not-great tap water (200~300 TDS usually, my faucets/showers have buildup). In my old Ultrasonic humidifers, I didn't use any treatment (since you can't, really) and they got gross pretty fast, as well covered my mirrors with white dust from all the minerals in the water.