An update and response to Gin:
We are still very happy with our earth sheltered concrete home, and it is performing as we hoped and expected. It took 18-24 months for the temperature to stabilize (it was cool to begin with as the concrete cured)and now our electrical bills are pretty stable summer and winter. During the shoulder months we do not either heat or cool as the house provides the stable temperature around 74 that we want. The biggest problem here in TX is with the humidity, not temperature, and the house cannot really help with it. So far it has not been enough of a problem to install a dehumidifier. The heat pump system works as expected.
There have been no concrete cracks or leaks at all. We apparently planned well enough that there have not been any major corrections or additions we want to do that do not have wiring/plumbing available to them.
We do not have any open houses scheduled, though it is due to no requests rather than any other reason. If enough people want to see the house we will schedule one. I would direct people to other similar houses, but there is no good list or registry that I know about. Maybe we need to figure out how to create one.
If people have specific questions I am happy to try to answer them.