Product review (5 stars): Outstanding high quality instrument at a low price.
I bought two meters for use in my basement and shop.  I took them to work and compared them to a recently calibrated / certified meter in a room @ 50% RH and 72F.  They both read within 1% RH and 1F of the certified meter.  I did not check them at other conditions.  However, given my work experience with Extech equipment, I believe they would be accurate.

The low price, Dew Point alarm, min/max temp/RH, and easy to read numbers make this a outstanding instrument.  I'm a Ph. D. organic chemist and a stickler for accuracy.  High marks for scientific work or instruments don't come easily from me.

On a side note, the analog Relative Humidity gauges found on most consumer products are worthless.