What is there more to say, about that monster lens. Always wanted to have one. Back in 2004 I finally bought my first prime. Back then I was still a Nikon shooter and the 400 f 2.8 was a brilliant lens, although shooting mainly Aviation stuff with it, I was missing some important mm at the end.
Then I made the costly switch to Canon (which was the best move ever) and about 2 weeks ago, after about 2 years without a prime lens, I purchased the 600mm f4. I just got back from the Dubai Air Show 2007 and all I can say is WOW. You get what you pay for. This lens is sharp, sharp and sharp. I was surprised that you can even handhold it for a couple of shots.....
Panning shot at 1/15sec not a problem, thank you IS. Attached to a Wimberley Head the 600mm f4 is almost weightless and a joy to work with.