Hi,
Here are some video's of the launch control feature on the 335i. I know they are a bit fuzzy and the camera man shakes a little (it's bl**dy cold in Scotland today) but it will give you an idea what it's like.
PS. Much more impressive when your in the car and the back end is snaking about.
PPS. Once the car is heated up you can do it as many times as you want. No need to drive 6 miles between launches as the manual states.
Anyway enjoy