Great lens. Costs a fortune. People are always saying, go with the 70 - 200 f 4.0 L. It's lighter and more affordable, yes, but that's where the comparisons end. Read the lenstip review if you don't believe me.
Incredible images; Image stabilization....wow....I hear and see all these comments about how people should use tripos or use stabilizers with a telephoto lens of the length; Well I would have to say that, I cannot shoot hand held video without tripod or stabilizer on any of my L lenses except my 24...
No kidding it really is heavy; It is the only lens that I own where I can feel a bit of "play" with the way the lens fits on the body; I actually feel a bit uncomfortable carrying the of it around with just one hand on the camera body; I use a mark iii 5d