Product review (5 stars): Inexpensive, accurate enough, but a little slow to update
I bought 3 of these meters and have been using them in my house for a month.  I found that they are very slow to update the humidity.  It seems to update the humidity maybe once a minute at most and it will only update by typically a percentage.  So if you take this meter from inside to outside, it can take 30 mins to an hour to get the right humidity measurement, but it eventually gets there.  It stays withing 1-2% of my expensive Hygrometer if they sit in the room next to each for long enough for this unit to reach the correct point.  After that they match as long as they are near each other.

The temperature measurement is also always within 1-2 degrees of accurate and is faster to update than the humidity.

So for a mobile unit that you are going to move around, it isn't very good at all.  For something that will sit on a desk, night stand, or low wall and stay there, it works fine and is inexpensive at around $11.