Product review (3 stars): Not too bad.
I bought two of these monitors about a month ago.  One of them had some scratches on it, but it wasn't too bad.  When I tested the two back then, they displayed almost the same temperature and humidity when set next to each other which was a good sign.  This meant that the two were at least consistent, and I think they both were displaying the temperature and the humidity correctly (when humidity is > 23%, explained later).  The clocks have been keeping a very accurate time, and I have not tried the alarm yet.
I have an old Acu Rite temperature/humidity (I couldn't find a model # on it) monitor which I used for comparison.  These two units show a humidity reading almost the same as the Acu Rite when humidity is between 25%-33%.  Outside of this range, Acu Rite is the one that stops changing.  HTC-1 monitors continue showing humidity changes outside of this range (when humidity is > 23%, explained later).  The temperature readings are almost the same, in any range between the three.
The two HTC-1 monitors have been in a finished basement about 30 feet away from each other.  Yesterday, it got very cold in our area, and therefore, humidity level dropped in the basement.  I noticed that both monitors showed a humidity reading of 10%.  I turned the humidifier on, and after a few minutes I noticed that the one nearest to the humidifier had jumped to a humidity of 29%.  The other one still showed a humidity of 10% which couldn't have been possible.  I moved the one showing 10% closer to the humidifier, and it suddenly jumped and showed a reading in the twenties.  I moved it back, and it dropped to 10% again after a few minutes.  I finally figured out that the units apparently show 10% humidity reading when the moisture level falls below 23%.  I put the other one in the same spot where one was staying at 10% humidity reading, but that one never got to 23% or lower.  So, I can say that one of the two broke after about 3 weeks of usage, and the two are not very consistent now.  Well, as of now, one is considered broke when humidity level is less than 23%.
Another observation I made has been that these units show changes, both temperature and humidity, very quickly.  You can pick one up and hold it, and you can see changes in temperature and humidity in about 30 seconds.  This is actually not a bad feature, in my opinion.