Product review (5 stars): Work well and can last if you care for them
I use two of these vornado humidifying units to try to decrease how much I use A/C.  If you live in a semi-arid environment they really do work well in single rooms.

But, you have to be scrupulous in terms of keeping these units clean.  Don't leave water in them unused, clean them thoroughly with bleach water at least once every couple of weeks and either change these filters as often as recommended or carefully disinfect them in dilute bleach water.  They can last a bit longer if you are careful (and consider purchasing the silver ball disinfectants for the tank).