Other than being surprisingly light (2.3kg is pretty light for a lens like this) this lens is one of the sharpest you can get your hands on. If you're photographing wildlife at short-medium distance, this is perfect. And, because the lens is f/2.8, it works really quite well with Canon's 1.4x III and 2x III Extenders.
And of course, as you'd expect the optics, build quality, focus speed and focus accuracy are all outstanding. This is not a cheap lens, but you won't be disappointed.