This is the “all around” supertelephoto. It’s a significantly smaller and easier to handle lens than the Canon 600mm f/4 or Canon 400mm f/2.8. It can be shot from a sturdy ball head while the larger lenses really require a gimbal head, and it can be shot handheld for at least a few shots before your arm gives out.

And now, it’s been replaced by the new 500mm f/4 IS MkII. But while supplies last, this gives you a really good supertelephoto lens at a much lower price than the new version.
March, 2013