If you have any examples of direct comparison, that would be great...
Direct comparisons? You mean shoot this scene, put the one camera down, shoot the same scene with a different camera? I'm afraid that would be impossible. If you don't want direct comparisons, the internet is littered with shots from a 1D4/400mm combination sports shots and there are a number on my web site.
And sure, I'm willing to admit that part of my glee is due to the lens, but I also temporarily shot with a d7000 and wasn't nearly as smitten. I was going to get a D4, but full frame 16.2MP just wasn't going to cut it. I used to shoot important events with a 1D4/400 on a tripod and a 7D/70-200 f2.8 II on my shoulder for when the action got close. Now I'm hand-holding everything with just one camera and getting great shots.
Canon doesn't really have an answer. I have explained this before, so if you've read it, move along. There's the vapor-lens 200-400/f4 +1.4x that I had been waiting on for the better part of 3 years, but the pricing on that looks to be more than what I paid for the d800 and
the 200-400/f4 lens. Then what would I put that lens on? A $3500 5D3? That has no advantages. A 1Dx? I suppose that might be killer, but to get the reach of the d800 I have to drop in the 1.4x and then I'm at f5.6. And then there's the small matter of the $6800 price tag of the camera. The MSRP of the Canon 200-400 + 1Dx looks to be approaching $19,000. I paid almost exactly half that. Half!!
Plus this lens still doesn't exist... and neither does the camera. Some will say "nobody pays full MSRP for lenses." Well, yes they do. In the first year or so when they come out, the big lenses sell at full price, if you can even find them. The 400/2.8 II is still $11,500 at B&H and Adorama, despite being out for some time. It may come down in a while but how long do I wait. Until 2014?
I'm not crazy. I'm not needlessly berating Canon with my shrill hysterics. Others will do what I have done. Many others.