Product review (4 stars): It requires maintenance every year or two.
I see a number of people have given this a bad review because it quit working after a year or two.  Being a mechanic and a person who has built a couple of houses Im not going to throw something out without first trying to fix it. I found that every year or two I would have to wash the dust and dirt off of the plastic (moisture sensor) strip inside. Running hot water and a little bit of dish soap over it and then dry it gently with a hairdryer. Be sure not to allow the plastic to wrinkle up. Works fine every time afterwards.  Even your furnace needs to be cleaned annually, including the flame sensor,  along with fresh filters twice a year.

Fix it, don't replace  it.