The Canon 100-400mm is a great lens. I have a 70-200mm 2.8 but I bought the
100-400 4.5 to get more reach when photographing wild life. When shooting with my 7D, it is equivalent to a
160-640mm lens. I have always thought of the 70-200mm 2.8 as the gold standard in zooms, but this lens is right up there with it.