Product review (5 stars): Accurate and easy to read
I am a physicist with a new zone in my forced-air heating system and a piano that needs to have constant room humidity, preferably around 42%.  I bought three of these monitors to assess these conditions.  The first thing I did was to enclose them in an transparent, air-tight container with three other humidity monitors that I have been calibrating for years.  I put the container next to the room thermostat and noted the readings 8 times over the course of 30 hours.  I opened the container twice to let in air with a new humidity.  Heres what I observed:

1. The readings stabilized within about an hour or two after each time I opened the container.
2. The 3 new monitors agreed with each other to within about  0.5 F and with the thermostat reading.  This is more than good enough for me to use to assess the uniformity of the temperatures in the different rooms of my new heating zone.
3. Their humidity readings agreed with each other to within 1% RH.  Thats excellent  but possibly inaccurate.
4. Comparing the humidity readings with my careful calibrations of the other humidity meters, I concluded that the humidity readings of these new monitors are about 2% higher than the true humidity  at about 42% RH.  That is excellent.

Therefore, I scientifically conclude that I am happy with this purchase!