All in all this lens is a superb package and is one of our most popular lenses. It's probably the best hand-holdable telephoto zoom for Canon SLR's. For wildlife, motorsport and aviation - it will perform brilliantly.
This lens can be used with a Canon Extender (teleconverter). The 1.4x Extender makes it a 140-560mm f/6.3-8 zoom, which will still autofocus across the entire zoom range on EOS 1D-series, 5D Mk III or 7D Mk II cameras. It is also physically compatible with the 2x Extender, which makes it a 200-800mm f/9-11 zoom, but that combination is manual focus only.