On the Boxster, you don't have to release the key to disengage the starter, the starter is released automatically once the engine catches. This eliminates the possibility of over-running the starter and damaging the bendix or ring gear - the whiney, grindy, sound you hear if you accidentally turn the starter switch when the car is running (on other makes).
Because of this, you need to reset the switch each time you want to engage the starter by returning the key to the '0' position, then the starter will re-engage when the key is turned to the start position.
This feature is becoming more common on other makes too, my wife's Jag does the same thing.
