Product review (5 stars): A cleaner humidifier
I've been using the metal filters that came with the unit.  After a couple of seasons, the metal starts to disintegrate.  The material in these permawick filters seems to stay clean.  I empty the water each week and clean the tray of any matter that might build up.  The tray would get quite dirty with the metal filters. The permawick filters keep the tray much cleaner and cleaning is no longer the chore it once was.  I will by new permawick filters at the end of this winter season.  Good product.
Additional comments: It is now 2/11/15 and I have ordered two new sets for next year.  These are really good filters.  One problem I had with the original metal filters was that they had to be positioned precisely to avoid hearing a dripping sound.  These filters eliminate that problem.  Can't say enough good things about them.