Product review (5 stars): I'm glad that I read some of the reviews first
I'm glad that I read some of the reviews first, because some people felt that this little thing wasn't accurate until they'd waited for a short time for it to 'acclimate' to your room, which was a good thing to know.  We'd just bought and moved into a house that had been sitting empty for awhile, and I was starting to worry that the thermostat on the wall wasn't accurate; it was set at 80 degrees (in Florida, in August) and yet the house was comfortable, and even chilly at times.  I was certain that our first electric bill would be a doozy, and was really starting to worry that the correct temperature was 10 degrees off.  But this was the best little gadget buy of the year.  Probably within a few hours or less it started showing me the correct temperature, but it wasn't until I kept checking it repeatedly over several days that I could relax and trust it - and it's always giving me the same number that the thermostat on the wall says (sometimes within a half point, but on the other hand - my thermostat on the wall doesn't show points).  I'm very glad that I bought it and highly recommend it!