Product review (5 stars): Good Product, Try Cleaning Before Replacing
Reasonable price at about $40, that is 1/2 what they are asking at the local supply store in my area.

I've noticed some giving poor ratings due to the tendency these have to clog.  I have had the same issue, and I think it has to do with the months of non-use during the summer, corrosion tends to built up, but I found a simple solution. Try this before replacing every year or two.

I turned off the water supply and removed both lines (in/out), then turned on my furnace and turned the humidifier up so that the valve would activate.  I sprayed a good dose of cleaner (I used Gun Scrubber) into the top opening.  I turned off the system and reconnected the lines, fired it up, and water started flowing as if it were brand new.  I figured if Gun Scrubber can clean carbon out of a weapon, it might work for this application, and it worked perfectly.