I will try to post some photos this weekend. However, after just having the 200-400 on a safari for 2 weeks, I can't understate how incredible versatile this lens was. During one shooting "session" I was photographing lions and cubs at 400 with the extender. A couple of lions from the same pack took down a zebra about 150 yards behind our vehicle and, as a result, about 8 other lions stood up and started to work their way towards and then right past our vehicle to partake in the meal. Without switching camera bodies or lenses or even really moving much from my original position in the vehicle, I was able to photograph each lion as it got closer and closer. My other friends were fumbling to switch camera bodies back and forth (missing shots) or found themselves very limited in their composure options as the lions got closer to the vehicle. The minimal focal distance was also a big advantage when we came up on wildlife very close to the vehicle.
I'm not saying the 200-400 is better or worse than any other lens. I am saying it definitely has its uses. For those particular uses, I don't think it can be beat.
That is what impressed me about the lens, the very versatile focal length - 200mm to 560mm. From all accounts it has very good image quality at all settings.
As I don't do sports serious, I don't necessarily need f/2.8 - but as I DO wildlife photography - including BIF, and also love the 'tele-compression effect in various landscape settings', I would find the 200-400mm f/4 1.4x very useful.