Since the Model S is so quiet, there will be no audible feedback on your speed like an ICE car, or even a Roadster. Leaf owners tell me it's all too easy to get going too fast unless you use the cruise control. But of course unless it's adaptive cruise - which isn't available on the Model S - you can't use it in traffic. Sounds like a recipe for speeding tickets.
I think there is a trivial solution: a simple app for the touchscreen. Whenever the car exceeds a certain speed it goes "bong". It should have buttons to turn on different thresholds, which would all be user-programmable. (I'd make them toggles so you can leave them on if you like.) You might set up buttons for freeway, regular highway, and city streets.
So let's say you pull onto an 80 kph highway. Everyone goes a bit faster than that, so you'd have a 95 kph button (or whatever works for you). Now if your car ever exceeds 95 kph, you get a polite "bong" to let you know.
I think this simple feature could save Model S owners a lot of speeding tickets.