Product review (2 stars): They were Wonderful Instruments
Well, I just bought a new model, the 00611A3-ex and am very disappointed.

I asked the co. if the unit would read from my old sensor, as I didn't want two different sensors on the table on the porch.

Took them two weeks to answer, yes it would.

So I bought it (not from Amazon) and found out, no it won't.

Not only that, although this unit cost more than my old units, it's functions have been downgraded.  The old units included on the display the high and low temps for the day.  The new one doesn't, you have to push tiny little buttons on the back to temporarily display each separately.

Further, the new one is, indeed inaccurate compared to the older ones, and to a pretty good thermometer I used to check all of them.

Lastly, the outside relative humidity reading is stuck on 99%.  It won't move.

I'm returning it.

Initially:  I have had two of these for several years, and previous models also, and have always found they work well, subject to two caveats:

Keep the sensor out of the sun.  It will definitely read inaccurately if the sun is heating it up directly, it's to measure air temp. and humidity, not heat from the sun.

Micro-climates - the climate at your house is virtually never going to be what they report from the airport, even if you live by the airport, or from other weather bureau stations or even satellite measurements unless they are measuring from where you have the sensor.  With these you can discover what your micro-climate is.  For instance, my shaded screened porch is usually about 2 degrees more in the winter, and 2 degrees less in the summer than what the weather service is reporting for our area.

Why?  We are completely surrounded, 360 degrees, by trees.  We're in the middle of a 200 ft diameter circle.  Not only do the trees (and the meadow inside the circle, we don't have a lawn) greatly affect the temperature, they also break the wind.

Our humidity in the summer is a few points higher than the weather service reports, about the same in the winter.