I bought my first one about two months ago. I am so impressed by how well it works. I live in the Phoenix, Arizona are and I can see all the dust it collects on the outside pre-filter in just a few days. And it is so easy to clean the outer pre-filter!! I just use the hand attachment of my vacuum cleaner and pass over it for a few seconds. One warning: The high speed setting is a little louder than I was expecting. Other than that, I love it and I have started buying it for other family members and friends. I think it would make an awesome gift for anyone - especially people with any sort of breathing issues.