VdV. Only been at the commercial game for 5 years but I've never been asked to either state or fly to a ground speed. Occasionally if it's a breezy day and you are the first aircraft to arrive at an airfield for a couple of hours the approach controller may ask for various wind readings through the descent. They only see our speed over the ground on the radar but control us by asking for adjustments in our indicated airspeed. The knowledge of the wind direction and speed we are experiencing helps them out with that adjustment. In the cruise we try to operate at the most economical speed for the aircraft and if that doesn't suit the controllers planned seperation may be asked to adjust IAS or Mach, but never ground speed (so far)!