Just wanted to mention that we have had the Rabbit Air for a couple of weeks now and I ***LOVE, LOVE, LOVE*** it! Ran it on high for a few hours after it came, then put it on Auto. It is very quiet, especially since it is usually on its lowest setting during the night. I no longer wake up with the thick congestion and cough that has been getting gradually worse over the years. It did not solve all of my dh's problems (he has a lot of sinus-related issues), but it did seem to greatly reduce the headaches he was waking up with every morning (and my headaches are gone).
My daughter is using the large, round Honeywell brand Hepa air purifier we bought years ago. It really helps with her apartment. However, it is large compared to our Rabbit Air, and definitely more noisy. She will keep it because it doesn't require regular maintenance on her part (occasional removal and washing of the charcoal filter, and perhaps annual replacement of the Hepa filter in the machine). The recommendation for our Rabbit is to wash the pre-filter once a month and the Hepa filter every 3 months. This is not a problem for dh and me, but my twenty-something prefers not having to do that.