People need to realize that the way faster AF isn't to be taken lightly. This has little or nothing to do with aquiring focus at a still subject. When my son starts running and stopping and going side to side up close there really is no contest whatsoever. The 5d3 could get better hitrate than the 1d4, but it's first now with the 1d X that the Case 1 through 6 really starts to mean something. I can't miss a shot with the 1d X .
And the metering people say "well, 3k for a little bit better metering" is FAR from little better, it's DEAD ON every single time and helps out a great deal in the tracking process. Plus, as mentioned by others, it makes for no correction of exposure in post, which gives less noise. I have offset the 0 EV in camera to +5/8 of a stop, because I like things a tad over and can always pull down for even less noise.
I agree that unless the 1d X is tested, and you only read about it, I too felt it wasn't worth it. Now, after owing it for a while I can safely say, the distance between the 5d and 1d is still huge...
I loved the size of the 5d3, but the grip is sooo much better on the 1d. And to have it flip vertically and feel the exact same is also huge.
And on top of that, it's the 12 fps, all the little things like AE tweak, spot-meter to AF point, no mode dial, so I can deselect all of the drive-modes I never use (I have only H and L burst available, set C1 to bracketing with 2 sec delay still works). The powerbutton in the right place, dual CF, and not only 30mb support for SD. Replaceable focusing screen, although, currently, no support for the one I wanted, namley the EC-S. Better options to assign buttons to other functions. Shortened release lag etc etc.
My favoritefunction though, is the abillity to set which two shutterspeeds I would like the camera to work between, that way I can shoot Av and NEVER get too long a shutter.