Product review (4 stars): Good bang for the buck and accurate from 1 unit to the next
I have purchased 4 and am pleased with the purchase.  Relatively inexpensive.  I was curious about the variability between units and found that they were very much in line with each other, which is terrific.

To determine variability between units, I placed all 4 next to each other and left them idle for a couple of hours, after which they were all within +/-1 % humidity of each other and +/-1 degree each other.  That seemed good to me given the relative low price of these units.  Temperature also aligned with two other thermometers I had in the room.  I can't speak to absolute accuracy of the humidity detector, as I have no other way to measure humidity.

Only slight knock against this is that the rating for the humidity ("low", "ok" or "high") appears random.  Sometimes something like 53% will be deemed low, sometimes high, sometimes OK - all with the same temperature.  Perhaps there's something I'm missing, but I don't know what it is.  I simply ignore it because I don't need it to tell me what's good, but it's kind of annoying.  Still, it wouldn't stop me from purchasing more.