Received our GermGuardian the other day and plugged it in right away. My wife and daughter had been dealing with allergy issues, and within 24 hours both of them noticed a difference. We've placed it in our living room behind a chair, and there is no noise noticed. We have it set on level 1 and it's doing it's job. 

Pros: Truly cleans the air, not an ugly item
Cons: level 3 is noticeable.