Interesting results. Very long lens! I wouldn't mind 600mm for wildlife. It is probably heavier than I'd be happy to carry around though
My wife and I have shared her 100-400L since she bought it in 2004, I'm looking forward to when the new one is actually released to see if it's lighter and by how much.
I have often thought of forgoing all of the above and getting a 200mm f/2.8 L + 2x tele. End up with a very lightweight 400mm F/4 lens.