These are doing their job well, so no real complaints. Air is noticeably cleaner, and machines are simple and unobtrusive in their rooms. The only negatives I would have would be in comparison to two other units of different brands we bout at about the same time. 
Noise: the lowest setting is fine, the second lowest setting is just in the edge of fine - loud enough that you notice it when you walk into the room, but disappears when you turn in the tv. Above that setting, it is LOUD. So if you won't get the cfm you need from the first two settings, you may want a different unit. 
Smarts: you turn these units on, you set their level, they run and tell you when the filter needs changing. All fine and completely functional. But compared to our other units, which turn up and down in response to need, and have different night/day modes, these seem a little stupid for the price. 
I like them, they are good, but I'm not blown away.