Wanted a small appliance like this air purifier to use in seperate bedrooms to stop dust/pollen/dander/dust mite poop or whatever debris lingers in the air from being inhaled during my loved ones sleep, this one works great and appears to really remove debris from the air. I am sure that higher priced air purifiers with expensive replacement filters work much better but we did not want to pay $$$ plus $$ for replacement filters three or four times a year.
On low the fan can barely be heard, medium is like a normal fan noise and is not bothersome at all (all of us stated we actually enjoy this white background noise), high would be too loud for most sleepers. Each of us that have one in their bedroom merely turn it on high an hour before bed, then turn it to medium for actual sleep time.
Can be layed on its side or stood straight up which is a nice choice to have based upon personal preference.
Filter is easy to remove and clean, just wish HB would have made the material surrounding the filter a bit more sturdy as it is just thin cardboard so you have to be careful not to damage it when cleaning. I use the brush attachment on my vacuum cleaner and it works great. I highly doubt this filter would be permanent like HB claims after many repeated cleanings so we expect to replace it every couple of years just for good measure!
Overall I gave it 5 stars but it surely would not compete with a much more expensive winix or austinaire, regardless, IMHO, it is an exceptional value for the price.
Edited to add: FYI, to dramatically enhance the effectiveness of this unit, go to a Lowe's or Home Depot type store and purchase a sheet (hammock filter) of the 3M filtrete filters (about $18 bucks, the good ones, the type used to put over window airconditioners to trap allergens/dust). Cut a square large enough to put above/over the permanent filter on this unit, the filtrete filter then takes most of the particles before it even hits this unit's permanent filter. I have done this for 4 months, it does not damage or negatively affect the unit's motor and you will be amazed how much stuff these little units take out of the air (with two filters, a filtrete one and the one that comes with the unit). Best part of all, after two months, merely discard the 3M homemade filter and replace it with a new cut-out. I also discovered that I can merely lightly tap the unit's permanent filter on a hard surface outside and it is ready to go for an other two months. I think you could get about 16-18 cut-outs per sheet at $18 per sheet, it is enough to last 32-36 months (approx 6 dollars a year).