We bought this ultra sonic unit for use in our master bedroom since it seemed it would give better coverage than our smaller unit in such a big room. Ultra sonic distribution is finer and the tank lasts longer because the mist comes out with a lot more control and a lot smaller particles than cheaper units than don't have the ultra sonic feature. We love this unit for this particular ability that it has. Output Volume A tank can last us two nights with average output or a full night with NO problems (and no refills needed) even on heavy output. We like this as an extra unit in a child's bedroom if we want to run it all hours of the day. We don't have to fill it up very often. Performance It works very well. We like the fine misting ability. We like the larger tanks and amount of volume it will hold. You can also put additives into your water for any type of health benefits you're looking for. Ease of Cleaning Not as easy to clean as more basic models that have openings that allow you to fit your whole hand inside to wipe all the surfaces. For this unit, where I can't do that, we tend to let the filled unit soak with a dilute bleach solution for a few hours to make sure we're killing any bad bacteria or mold that might be growing inside whenever we use it frequently. Durability So far, so good. We've been using it almost continually since before winter to counteract the dry air our house has in winter due to a wood stove. Design Okay and nice to look at.