It really varies. My wife had a C300 and it was pretty seamless and didn't bother me. On her X1 it is brutal. It shuts off prematurely (before you're even completely stopped) and it's a DCT trans so when it starts back up, it takes a few seconds to get in gear and let the clutch out again. To disable it, you have to dig through a few layers of menus. We added it to the shortcut screen to make it easier, but it's still super annoying.To be honest, the auto stop/start is the least inconvenient thing ever and amazes me how badly it irks so many. I had it on my Mini Cooper S and it was easy to control. I also have it on my current Forester which again is easy to control when I come to a stop.