I`ve searched and read a little on this combo, but I`m not sure that the focus speed is very useable especially since fast AF is needed on what is a 300mm equivalent. Any views on this. Given the price of this lens compared to the Canon and Nikon equivalents, it almost seems like a E5 body might be a good buy to run this combo? Any views versus the Canon/Nikon output? Is either Oly combo easily handheld for walk around shooting?