Has anyone ever use an air purifier? Does it really works? How's the value for money? I have sinus problems and i was hoping it might help. In today's TheStar, there's a few articles promoting it notably the Honeywell and the Medklinn brand. I'm kinda leaning towards Medklinn (http://www.medklinn.com.my/index.html) since there's no filters to replace or clean and you just turn it on for 24/7 operation.