I use 2 in my bator, and neither are the built in ones. One is an indoor/outdoor with a remote sensor, and the other one is a mercury one. The digital remote one does not go to tenths, but the mercury one stay real close to 99.5, the remote one bounces between 99 and 100. Holds very steady...
We will see, I just set 31 Black Jersey Giant eggs in one of the, with all the accessories. My last hatch was a total failure, so I bought this bator to see how it works. I will be building my own bator in the next year or two though, as I have some ideas I would like to implement.