I wanted to start this thread to see what people have observed and to ask questions about their Model S. I will start out to ask this one. When I am driving on the freeway and have to slow down for traffic, I take my foot off the accelerator. Does my brake light come on or does it come on only when I press the brake?
Yes, the brake lights do come on when regenerating at moderate to high levels. You can see when by touching the battery icon to display the "charge" screen. The image of the vehicle shows the rear hatch brake light and will illuminate on the screen when the lights are activated--even when regenerating so you can see when they are coming on.
Yes. What he said ^
Press the battery charge icon to see a real-time display of what your car is doing as far as lights/signals. The program that Tesla uses to engage the brake light is more advanced than I originally thought when I first bought the car. There's some kind of G-metering system because even when you go completely off of the accelerator and have full regen happening, the brake light does not turn on if your momentum didn't change (say you were at freeway speeds and were going downhill). Basically, if you can feel any drag on your car at all from the regen braking the brake lights will come on.
Oh, and I've never liked being a creep (enabled kind of guy)