I love those air purifier.  First and foremost, when using just the purifier option, it is super incredibly quiet!  When using it as a heater or AC, it makes white noise, but no louder than any other good quality machine out there.  Here in NC, it's nice to have the heat option for when the temp goes down to the 40s at night and you want a little bit of heat without having to use the entire HVAC system.  This thing is a behemoth though.  It's 2.5 feet tall and I call it my R2D2.  And to finish it off with the coolest thing ever... When you turn it off, it sounds like the first several notes of Sesame street!