I test drove an M3 SMG. The car was backed in on an incline and when I let up on the brake, it rolled back a little, so I quickly reapplied the brake. I pulled back on the left paddle for a couple of seconds, let up off the brake, didn't roll back, and off we went. I had to explain this to the salesman!! Unbelievable, he did not know of this feature. It was a pre-owned '03, already broken in; I should have shown him launch control-lol.