Product review (4 stars): Not bad considering the price. Tested within tolerances compared with existing Thermo-Hygrometer and digital HVAC thermostat.
Ok, so lets level set and understand that we're talking about a double pack for <$20. That being said I would say these are fine for general use if some variation in the humidity or temperature is acceptable.  I purchased these to get a reasonable feel for the humidity/temperature in a couple outlying areas of my house and was not looking to spend $40+ for a single, potentially, more accurate thermo-hygrometer.

Reading some other comments on how these are terribly inaccurate, I think you must understand that there are tolerances in all of these devices. This one specifically +-2 degrees for temperature and +-5% for humidity. I found that these were within tolerance compared to an existing thermo-hygrometer and my digital HVAC thermostat.

Again, if your looking to not spend too much and are not needing to be within 1 or 2 degrees of accuracy, then these should be adequate. If you need a higher confidence of accuracy, then spend more money.