... For people who intend to shoot some action pictures as it happens so often in real life (young children playing at home, Dogs running and playing, Indoor school sport, ) or even shot in the night when travelling in cities without tripod ... that zoom is slow, I can't find any use (I sold my 70-300DOIS for such reason too many limitations in real life) ..
Basically, even @f2.8 you've got so many limitations (for action you often get ghost hands, feet, hair, balls) that you need a body able to shoot @6400 to reach the minimum action speed of 1/800 .. Even for portrait DOF range is almost inexistent. So just for landscape and walkaround outdoor and daytime it's rather poor as uses range.
So new 70-300L is somewhere ........ nowhere