When I saw this picture, the 600mm handholdable as the 500mm really is questionable. My biggest complaints with the old 500mm, physically I was glad it isn't any longer. Loosing weight was a good thing because when you hand hold something that heavy off hand it is hard to steady. Two stops of IS wasn't enough.
2012-Canon-Big-White-L-Lens-Family-Picture-with-Hoods.jpg by hdnitehawk01, on Flickr