I use the RabbitAir -- it's good, but I don't clean it as often as I should, so I'm not the best judge. It uses the layered approach, so if you don't clean your outermost filter, then it clogs up, and the second layer has to start doing the work of the first. My only complaint is that it will only ever shoot air upwards -- it's only quietest when it's on its lowest setting, so I would like to have it shooting directly at my face when I sleep. And I can't. It's still quieter than the Honeywell QuietCare that I used to have, but not by much.