The Canon EOS-1D X is a remarkable camera but it does have some annoying features that Canon should look at and try and correct with the next Firmware update, in my opinion. First, it does not AF with apertures smaller than f/5.6. This is particularly annoying to me because I usually travel light when on photo shoots and rarely bring big tripods or faster and longer, 'Big White' lens like the EF 400mm f/2.8L IS and 500mm f/4L IS. Being a full framed camera and adding the Canon 1.4X III extender only provides me with a focal length of 560mm when I shoot birds handheld with my EF 400mm f/4L DO lens. As any bird photographer will tell you, one can never get enough focal length. That's why I always bring the Canon EOS-1D MK IV with me as well because it can AF down to f/8.
The second annoyance is less of a problem but still needs fixing. The AF points on the EOS-1D X is black. The only EOS-1 series camera in recent years with that. Fortunately, it is similar to the EOS-7D's AF points. When the 7D first came out, I had a tough time adjusting to its black AF points but now I have acclimated myself to its peculiarity and so the 1D X AF points are 'bearable'. Friends of mine have differing opinions on these annoyances but changes to the top of the line camera should be gain acceptance quickly and these two features are not very well received.
I have now received my EOS-1D X camera and have put it through a rigorous, real world photo shoot in Alaska and Canada. Click here to read my review of the camera and visit my website MichaelDanielHo.com to see many exciting wildlife shots taken with the new gear.