I think it is such a shame that canon stopped catering for the professional studio photographer. When they came out with the first 1DS, many professionals threw away their MF gear and got that. Even the 1DX still seems to carry so much film EOS DNA, which I thing is really blocking them from evolving into a modern system.
I like what Sony is doing with the alpha 7 and 7r, they manage to move on and leave things behind that are crippeling them. .......snip
I'm a big fan of mirror-less, completely blown away by the video quality of the Pana Gh3's, have the OMD e5 for some stills and like most people find the development of the new Sony fascinating.
Though I still own Canon 1dx, 5d2 and 1ds and a large amount of glass. Why?, because if you work all day with a mirror-less evf, (and they are getting much much better) and doing a dedicated still shoot, the Canon is so refined, with zero glitches.
18mpx seems small in todays 36 mpx world, but I've compared the 1dx files next to my two 1dsIII's and really compared them and found the 1dx had more real detail, plus it shoots at a crazy frame rate of like 10fps, shoots beautiful raws and jpegs, amazing autofocus, tethers bulletproof in DPP with ethernet (like nothing I've ever tethered before) and when it's all said and done, it's not a revolutionary camera, but it's a highly refined still camera.
Recently shooting a combination motion and still project, it was much easier just to continue the stills with a GH3 or Olympus because that's what we were using with some of the video, but after using an evf, going to the refinement and robust size and build of the 1dx made a huge difference in ease, file quality and results.
We all love big new development but refinement really makes a difference and the continuity of the line is huge in terms of keeping your favorite lens set and not having to search out everything new from filter rings, to shades to learning new software or even complex camera menus.
I think for the casual photographer a sony 7 is great, same with the omd, so is the panasonic, but when your in to one of those 20 set up, 2,000 frame days, where it's a billion degrees, no time for any equipment glitches, going from flash to continuous, 2 screen heavy tethering, a mirror-less compared to a tried and test ovf, refined 1dx, is like a having 200 lbs of agro lifted from you.
In fact that's where all of these reviews on cameras fall down. Sure people test the detail of the file, the focus accuracy, the color, tone, noise and accessories, added lenses using lcd focusing all doing casual walk about photography, but they don't test in the brutal conditions we work under, those times when a client must see the image in 27" splendor, the ability to tether and see the image immediately on a large screen while also on the camera lcd.
It's the same thing with my RED cameras and the Gh3. Sometimes I think why did I spend the money on RED's when the gh3 is so easy and so good, until it's very heavy production, you need 4 channel sound, cages that actually fit, finders and monitors that hook up professionally and secure, additional fan cooling, lens mounts that are tough and accurate, footage counts and file naming that is perfect and a dedicated software suite to process and you can rent anything for a Canon or RED in any market in the world.
Then you realize where the money is well spent and that the RED is ready for heavy expensive production, just like the Canon 1dx.
That doesn't mean mirror-less doesn't have a place or isn't getting better, because it is and for some things it's perfect, but in my view no evf dslr style camera is as robust as the large traditional workhorse dslrs.
Also we should keep in mind that Sony in regards to standard dslrs, has never caught up to Canon and Nikon so the 7 series is a place they almost had to go to gain traction in the market, but I'm not sure that a 2.5 fps camera with limited continuous focus is really ready for heavy lifting.