I just watched a German video of a test ride. The two screens looked very bright at night, a bit of a distraction. Do they auto adjust or dim when not being used at night?
Yes, they dim. Maybe an artifact of the camera settings or deliberately overridden for the purpose of the video.
The display has independent settings for day and night mode. You can set screen brightness for each mode.
Videos are not a good indication of actual screen brightness due to the way the light sensors in the camera work. Camera light sensors are, by default, calibrated to a "normal" scene. Some sky, some trees, a couple of people, and some grass. They assume that the image averages out to 18% grey. So if you take a picture of snow, as an example, it will turn out grey. A nighttime scene in a car will try to make the image appear as though it were daylight, this makes the screen appear brighter than the sun.
The screen brightness range is extremely flexible but will not allow a total blackout of the center display at night. 0% at night is actually usable on unlit highways for basic functions when you have learned what screen buttons you want to press. More brightness is necessary to read the small print on some buttons.
In the first few days of Model S driving, I found myself having to readjust the night brightness to be brighter at dusk, then lower it as evening progresses. A light sensor would help to automatically make this adjustment. Keeping the Controls screen set to Display at night makes this an easy change during a drive. You press Controls in the lower left corner of the screen, change the setting and then either press the X at the upper left of the window, or better yet, just press Controls again to make the control screen disappear.