Just tested ours today and it seems to do the same as you mentioned, flashing empty for about 15-20 minutes with 0 miles left, and 5 litres left in the tank but I suppose your right, better this way round than the other! I do miss the old fashioned gauge though!
That and my old MPG trip computer as this one doesnt change! Never once in my old car were two trips the same, but this has been stuck at 40.6 since I bought it.
Just doesn't seem to add up, with the current MPG often showing 60-70 and the usual 99.9 when off the gas - who knows, its fun to drive atleast!