For me, the largest things I would be interested in are how well the unit is insulated, and a heat source for the winter time. All other items are easy to add in just like normal "camping", meaning cook stove and such. I will have to check out the website and see if I can answer some of my other questions.
Thanks again for the feedback. So the Cave camper is made of composite panels: fiberglass, 1.5" of styrofoam, and another layer of fiberglass. Seams are avoided on edges when possible by a process where the panels are actually bent. That means less chance for leaking water or air. The door on the back is a thick, beefy door with a quality latch and hinge. So the insulation is really incredible. In the end, it's like you are inside a big cooler on the back of your truck.
Of course, you have options for heating or cooling. One eye opener for us was with a 40 degree night in Jackson Hole we never needed a heater while hanging out playing cards; just the body heat of two people was enough to keep the space warm. A small, plug-in electric heater is probably the simplest option.
For A/C, we've settled on a very different approach as you can see in the diagram below. There are two 3" ports that you hook up to an A/C / heat pump. One hose pushes cold/hot air in and one pulls air out. The unit we recommend is remote controlled and removes humidity in the process. When you unload the truck camper you pull out the A/C / heat pump unit and set it on a table next to your slide in truck camper. Since it's not mounted to the camper all you hear is the soft sound of air flow; there's no vibration felt inside the camper. Only a 1kW generator is needed to power the unit.
I love this solution but am curious to know what others think. In particular, if you need A/C, should we mount something small inside the camper? This adds vibration and noise but saves some on the hassle of set-up and take down.