I drive a lot in Germany, it is a joy to drive there because there are no speed traps, as a consequence people obey the law _more_ because the traffic signs mean something, you see a sign for 100kph then you go 100 because the road or conditions will not allow that speed (god help you if you get a ticket because you really fucked up).
I've never been in a car in Germany where the (German) driver drove 100kph in the 100kph zone. Ever. Typically, "100kph" means "120kph" at a minimum, unless there's a speed camera nearby, in which case they slow down just to pass the camera, then speed back up.
One thing I will say is that they NEVER, EVER speed through a residential area. When the 50 or 30kph signs show up, they WILL honor them (within 10% at any rate), and I do find that a refreshing change from the US where people by and large just don't give a fuck.. I used to live across the street from a school, and the road ended in a T-intersection (a concrete wall, to be precise) and it never ceased to amaze me how fast people would drive past my house. I lived on one corner, the T-intersection was at the other corner, the block was about 200 yards long, and tires would SCREECH at both ends.