Top fill, large capacity, easy to view and use, warm or cool mist, and adjustable humidity.
One of the main features I was shopping for is the use of essential oils. It's useless. The pad just sits there, behind where the mist comes out. The mist needs to blow through the pad somehow. A definite design flaw.
I would prefer they make a unit in which oils can be added directly to the water, as you can with ultrasonic diffusers. If it can be done with those, why can't they do the same thing with a big machine like this one?
And I wanted it in black but that isn't available.
Other than that, I love this machine.
I have a weather station in my bedroom and the humidity display on this machine is very accurate. It puts out a lot of mist and covers my large bedroom and it's extremely quiet.
I used the warm mist the first time I ran it and it put out very warm steam within seconds. Some reviewers said theirs didn't heat up but mine definitely did.
My last humidifier had an essential oil tray on the inside of the tank. It held very little oil and melted within a few days, rendering it useless. A few months after the warranty ran out, it wouldn't turn on at all. I hope this one lasts longer but I did get the 3 years extended warranty just in case.
I think I'm going to order another one for my grandson's room.