Bryan announced the interview with Brutus Ostling and his take on the new 1D X for birding. I found it to be interesting.
The link is here;
http://cpn.canon-europe.com/content/...he_eos_1d_x.do
One thing you can draw from this interview, is what you can learn from his pictures. The second picture of an eagle on the page was taken with the 1D X and a 300mm F/2.8L II. No matter what gear you have, there is no substitute for getting incredibly close, which he had to do for this shot.
At present I agree with his take on the 2x extenders and the AF of the 1D X not focusing at F8 that it does not matter. However, when the II versions of the 500mm and 600mm come out my thinking may change.