Product review (3 stars): Good product
You can tell it works almost immediately after you replace the filter.  Within the next day or two you will need to refill the water tank.  These replacements are a reasonable price..

The down side is the filters on the Vornado seem to clog fairly quickly, you don't get much more than a month or two of humidification until the filter needs replaced.  Also, out of the package the filters stink.  I don't know what the smell is, but its terrible.  Kind of a musty, chemical smell.  If you put it right into the dehumidifier the whole room will smell of it.  I actually open the package and let the new filters sit out in my garage to "air out" before replacing.