The new merc system actually starts braking for your when you lift off quickly. Its a "safety feature" that you adjust your driving style to. Then when you borrow the wifes car and are in a fast stream of traffic you lift off expecting the car to slow down and nothing happens! If you ask me there are too many gadgets around that a good driver does simply not need. (I did a rant on some of these
http://www.torquecars.com/news/car-technology.php a while back)