Bests & Worsts Reviews from Amazon

UPDATE MAY 2020: the unit began making a squealing sound from the fan that got progressively worse. I contacted Coway's warranty department but they wouldn't repair/replace as the unit was listed as "used", which was news to me, and the warranty applies to the original purchaser. I was the original purchaser! The unit came in Coway box, wrapped, sealed, etc... disappointed in my $500+ squeal machine. BE AWARE! UPDATE: 1st month in and going strong. I cleaned the pre-filter per the schedule, and also the air sensor with a cotton swab. Note that when cleaning the pre filter, I used the handheld attachment on the vacuum, it's wise to vacuum from the direction of the air flow, e.g. the "outside" of the filter, so as not to force the particles through the fine mesh via the suction. I hope this helps! My wife suffers from severe allergies (pets, pollen, you name it). We had tried high efficiency filters in the central air, humidifiers, regular vacuuming, to no avail. She was on a daily regiment of Allegra and/or Zyrtec, and a full night's rest was hard to come by. The Airmega 400 has completely changed her quality of life. We've had it for 4 days and there's no looking back! Room size: if you've done any research, you already know that the size of the room(s) determine the size of air purifier due to its ability to turn over the air in the space. The unit is rated at 2 air changes per hour at 1560sf, a very solid rating, If you have exceptionally tall ceilings, take that into account too. We intentionally have it in the bedroom to filter that area and the adjacent living space, about 500sf or so. It's handling that area very well. (We're now going to buy another unit for downstairs.) Size: It is a large-ish unit so check the dimensions for your intended location. For reference, think of it as the size of an end table. It intakes air from two sides and blows air out of the top, so it needs free space on each side and you obviously can't put anything on top of it. Noise: in sleep mode, it's unnoticeable. We have a fan in the room which completely masks the fan sound as it switches from sleep to low. It gets progressively louder as it cranks up, but in our experience it has only turned on high when we've vacuumed or stirred up the elements. In the medium range, it's not much louder than the air coming through the vents of the AC system...not enough to draw our attention. The high setting is loud and the unit will move serious air but again it's only triggered for a few minutes at a time. Smart Mode: I have so far been impressed with its ability to sense changes in the air and turn up/down automatically. It works exactly as advertised. The LED indicator is helpful to see the air quality in the room. Sleep Mode: while the LED air quality indicator is nifty, it's too bright for the bedroom and we turn it off at bedtime. Again, the whisper quiet night setting is great. Cleaning: I haven't had to clean the unit but it seems straightforward to open the side air intake vents and access the filters. I did note that the filters fit squarely and securely in the unit with no gaps. The tolerances are well engineered. I didn't see the value in the app enabled "S" versions. I saved a few bucks and went without.