I had a play with a pre production 1DX2 today. Unfortunately they wouldn't allow me to take away any files to play with - NO FAIR!
However my observations were that the ergonomics have been improved over my 1DX, the AF seems even quicker (that's a real biggie for me!), the camera is quieter in all modes - not worried as my 1DX only scares people not wildlife! Looking on the rear screen there appears to be some very significant improvements in high ISO - but we will have to wait for real files that WE have shot to confirm this but it is looking very promising.
So far I am not convinced that it is really worth the upgrade cost - and I am staying with that opinion as I am quite certain that if I get hold of a production one and can really test it that my credit card may need CPR!
No conclusions so far, but it is looking very promising to me. We know it will be better than the 1DX (is that possible???) the only question is how much better? So far the AF alone has me twitching..............