FV-QR
Never heard of it for the MkIV. To answer this for anyone who comes across this in the future (note the original thread date) -- launch control was enabled for 2007-up vehicles in the US, and 2007-up owners who don't have it enabled from the factory can have a dealer enable it for you.
It's activated by putting the shifter in Sport mode, disabling ESP, placing your foot on the brake, revving to 3000 rpm, and then releasing the brake. You'll get a hard launch.
I've only done it twice -- once on an empty road (I checked carefully) to test it, and once in a parking lot to tease a few friends. It's mostly a gimmick if you aren't on the track but if you do track race, it's useful.
You WILL get wheelspin -- beware tire wear!