Thirty seconds to jot down three airfield elevations on a Mars bar wrapper beats fiddling with knobs....and in most locations the elevation difference is a moot point. Now if you are in an area where there is a really huge elevation difference one would not be able to set a QFE setting anyway. The Mark I Eyeball can work wonders in determining height and in theory should trump the altimeter unless one is truly addicted to "numbers on the clock".