I purchased then received the MinusA2 on June 5th (2019) and installed it immediately thereafter. I purchased an Air Purifier after months of health issues, which I couldn't determine the cause. Aside from hacking (coughing) which seemed to also originate in prior years, this past January I got sick with Flu like symptoms, which lasted for about three weeks. After recovering, I strangely had a relapse every few weeks, and eventually started having symptoms almost weekly, which oddly only lasted a day (coughing, fever, body aches, etc), knocked down with over the counter meds. Had 3 different doctor visits during those months, two different antibiotics (which knocked it down for for a few weeks after completion, but relapses again thereafter), two chest X-rays (each clear), and though never having any allergies, have been prescribed and tried different allergy meds with no difference. I travel for work, but never seemed to have issues abroad. When not traveling, I office from home, so spend the majority of time there. Also, my other half occasionally started to get the single day symptoms (oddly at the same time I did) in April/May, but works in an office so isn't home as often. So during the last few weeks of May, I started doing detailed investigation at home.What/How I tested:First checked air quality constantly throughout the house with a tester (PM2.5/PM10/PM1.0 Micron Dust and Indoor TVOC and other sensors). Since it seemed the issues were related to chest symptoms, felt they were most likely the issues, but nothing resulted in out of ordinary levels. I then tested our water sources, though knowing we've always had poor water quality in San Diego, we've been buying/using Carlsbad Alkaline Artesian Mineral Water for years. I checked that water, our bottled water dispenser (to see if any contaminants through the system) and did a thorough cleaning of the dispenser, though found no suspect ppm levels or other detected issues on any of the sources. We have pets which are very clean, and were already vacuuming constantly (robot vacuum and manual). Did visual checks throughout the house for potential issues (mold, A/C system, filters, fans, etc) which should have been detected with the tester anyways. Still suspecting the air quality, I decided to try an air purifier. Aside from the thorough filtering and good reviews of the MinusA2, I chose it over others for the unique wall mounting capabilities (very few out there), auto-detection, and degree of filtering for the room & adjacent kitchen area I spend the majority of my time, which is approximate 730 sq. ft. (unit advertises coverage up to 815 sq.ft. with 2 air changes per hour; allergy sufferers rated for 408 sq.ft. w/4 air changes per hour). I selected the Germ Defense filter model over the other three customized filter options.First Use:Installing on that Wednesday on a living room table to the side, I unfortunately had another relapse on Friday, but chalked that up to already having been affected. Immediately after installation, the sensor immediately shifted to "red" for high detection (checked with the tester at the same time, and still saw minimal/acceptable levels) and eventually shifted down to "purple" then "blue" over the next few hours. It would shift between levels at different times during the past two months, increasing filtering as it did. You could see it shift to red when cooking certain things in the kitchen for sure. I circulate the air in the rooms with ceiling fans, so it gets a good degree of overall conditions. I think it very helpful to have an auto-detection unit, rather than manually determining when you might need better filtering. I can happily report, after that initial relapse, I haven't had another recurrence since, during the following two months, with very minimal coughing issues, if at all. I did the first pre-filter & sensor cleaning a month later as directed, and all seems to be working well (will clean at the start of each month).Opinion:The unit has been about 6 feet away from where normally sit (until I mount it). The noise level is minimal, even when the sensor goes red and the airflow increases. Silencing the room and setting the unit to the higher levels, the highest Turbo was only 60dB from that distance, High was 54dB, and medium fluctuated between 50db and below (my meter just reports LO when below 50 so didn't test Low and Silent settings). I didn't mount the unit yet, as I wanted to make sure it was making a difference (which it is, in my opinion), so I probably will within the next month. I purchased the WiFi model to see and control elements of the unit. I've left the sensor set to default medium sensitivity level rather than raise it, though it's nice to have the option to change as needed (attached a screen shot of the app from today as I type this). The app is decently rated on Android with a 3.1 as of today, though only a minimal 16 reviews. Most of the issue reviews were problems getting the app and/or WiFi working, of which I had no issues, or wanting to see detection level history, since it mainly shows current levels and provides control. I will say, Rabbit Air responded to every single review (good or not), which is nice to see (I haven't posted a personal review yet). Aside from the manual cleaning of the pre-filter, the 4 filters are advertised as only needing replacement annually, and a complete set is about $95, which I don't think is bad (good to figure annual costs). You can see the details of the 6 stages of filtering on the product page. It's nice the unit has covers available with different colors and designs to fit the decor of a room, though I purchased the plain white cover model, but when mounted, plan to attach my own artwork. I also purchased a recessed outlet box for where I'll mount the unit, so the cord is hidden behind the unit (the back is flush without a recessed area for a plug behind; also plug is straight, and not 90 degree). I haven't used the timer (since it's been on auto since installation), and have left the mood light off (though when first installed the auto mode nicely shifted things off at night).My Pro vs Cons:Pros: Wall Mountable (flush behind, no recessed area behind unit), 6 Stages of filtering, large area air filtering/air recycle, Auto-detection sensor, Ease of filter changes & annual cost, Mostly flat front cover with designs available or possibly own designs (some con below), Overall very quiet, 5 year manufacturer's warranty, actual performance difference it made (for me).Cons (most minor personal wish-list things): Straight outlet plug - I purchased a recessed outlet box so won't be an issue but would be nice to have a 90 degree end, Front cover LED area is raised but flush would have been nice for designs, App needs detection history (at least for some duration; 24 hours, 7 days, etc), at 7-inches pretty thick mounted (filters box about 2.75in of it) but not bad considering performance needs.OverallI'm very pleased with the design and performance of the MinusA2, with some very minor criticism which wouldn't prevent me from buying the unit again. Hope this info was helpful to those making a consideration.