Upload & Sell: Off
For those considering trading in their 800m for a 600 II, I can't help but think that when Canon finally introduces the "next greatest" telephoto - the 200-400 f4 with the built-in 1.4x - that it will change the optimal combination yet again for folks like Arthur Morris who upgrade at every new introduction. I currently have a 300mm f4, a 500mm f4 I and the 800mm. If I was to make a change it would be to trade in the 300mm and 500mm for a 200-400mm which is lighter and much more flexible. (The built-in extender instantly turns the zoom into a 280-560mm which is a perfect compliment to an 800mm). The 200-400 would be ideal for zooming in on a closer, difficult fast moving target, and the 800mm would be ideal for pulling in a farther, slower/easier target. Owning a 600 II has the weight advantage of only a single lens, but it is not nearly as flexible as a combination of the 200-400 f4 and the 800 f5.6.
The estimated price for the 200-400 f4 puts it out of my budget, so I will be hanging on to my 300 f4 and 500 f4 I for now - both are excellent lenses and the 300 f4 has the additional advantage of having such a short MFD that I use it for semi-macro. But when the 200-400 f4 is available, I am guessing that Arthur Morris will change his tune about the 800mm. Andy Rouse swears by his Nikon 200-400 f4 (and his pictures are stunning), and the Canon version will probably make a big impact on wildlife photography for high-end Canon shooters, despite all the grumbling about the price from the folks who can't afford one.