I had an interesting opportunity on the weekend at the local model train show (where we help kids build cardboard train stations as well as give lectures on basic model railroading). There's lots of opportunity to photograph the fellows helping cute kids construct the stations. On Saturday I brought the A7r, 55 FE 1.8, and the 70-200 Canon L IS. Interestingly the latter worked better than the former, using manual focus to get eyelashes sharp. With the wider angle of the 55 and very poor autofocus. I hadn`t expected greatness, but considering the indoor soccer centre was decently bright, was more than disappointed with the number of failures (about 3/4 of the images).
So the next day I came with my Nikon D800E and 70-200 f4 lens and autofocused without problem and nailed the eyelashes 3/4 of the time which I thought very reasonable. When it came time to actually edit the images, though, shooting at ISO 6400 (ok, maybe it was darker than I realized but kids move fast) and wide open or at most f5.6, image quality definitely suffered. There isn't a fix for this currently - just a fact of life. The problem was less one of ISO than depth of field.
Now, the real reason for this 'test' was to see how the A7r would handle indoors photographing artists and musicians (part of our holiday) and the bad news is, NOT WELL.
The A7r would be absolutely fine for formal portraits, less fine for casual people pictures and hopeless for photographing indoor soccer (or equivalent).
Interestingly, I also had a particular model mine I wanted to photograph on Sunday so brought my tripod for the D800e - and after a couple of weeks with the A7r, what a pain using the D800. The viewfinder was dim. I switched to live view and had to put up with the terrible image on the lcd, swimming aaround, even after I turned of IS, and of approximately 200K visual information, vs. the 2.4 meg of information in the Sony Viewfinder.
I'm going to love the A7r for my landscape and industrial work.
I'm going to be interested to see how the A6000 does when it gets properly tested as using the same lenses and at 24 MP, it might be all I really need for the weekend's work in which case I can get rid of the Nikon.
My casual impression (looking at images on screen at 100%) is that shutter shake on the A7r with the battery grip is not a significant issue, and the bulk of the battery grip still makes the camera smaller and lighter than the D800e without battery grip.
Once again I have to say I was impressed with the 10-18 on the A7r - would I recommend someone deliberately run out and buy one for the A7r - NO, but if you have one already, for sure - and I'm not going to carry a separate ultrawide.