yeap i know what you guys are talking about. my 2005 c230k does the same thing when it down shifts to 1st gear i noticed that the car would slow down like and engine brake so i made a little researched of mine and i read that mercedes automatic transmission from the 2000 and up since the tiptronic. the torque converter has been change its hydraulically funtioning i think thats the word that they used well they said the clutch foot lever has been elimninated but it function the same with a manual tranny with out using your feet. its all robotic as they say. so when the car downshifts the robot that they call release the clutch and put the gear and then releave the clutch and thats why its kind of rough. and it is also the reason why they put that kind of torque converter is because this is the way how an automatic transmission can downshift while you stepping on the brake.