. . . has anyone actually run their bike until it ran out of fuel (deliberately or otherwise!)?
My gauge goes to the red and the warning light comes on at 160-180 miles, at which point I know I have a gallon left. I have made the modification to the fuel return to direct it towards the pump. I don't know though how much more range I have at this point.
Several of us have run out of fuel and written about maximum mileage experience here. It's not very interesting unless a deer is struck while doing it.
If you know you have a gallon of fuel remaining when your warning bulb lights then you know how much range you have if you have made an effort to compute your mileage every so often. You compute mileage by filling your tank, zeroing your tripmeter, riding until until your warning bulb lights, filling your tank again at the earliest opportunity, noting the number of gallons it took to fill the tank then dividing the number of miles on your tripmeter by the number of gallons needed to fill your tank when you stopped. The resulting figure is your miles-per-gallon figure.
Like Martin said, it can vary according to speed, terrain and whether the dangling fairing parts from the deer strike are creating excessive wind resistance. My K75 averages 50mpg but I'm not a trailbraking, high-siding throttlewhacker so that mileage might not be typical. I ride mixed mountain, hill and flat roads both gravel and hard surface.