Anyway, what I have discovered fits with much of what has been said and shown on the internet. Wide open the lens is exceptionally sharp in an image circle that reaches to top and bottom of the horizontal image but doesn't reach to the left and right edges (and definitely not the corners). Is this satisfactory for a 5X zoom, wide open (albeit f4)? I think so - most kit lenses aren't nearly as sharp or contrasty in the centre wide open and when zoomed half way to longest are already working at f 5.6 so I'm satisfied. The extent of the sharp image is sufficient for everything but landscape and architecture and those are rarely shot at f4 anyway unless you want a blurred background and likely don't care about the corners anyway.
At f11, critically sharp extends to the sides of the horizontal image and only the furthest corners aren't quite sharp - a lot better than wide open, and probably not even noticeable in a 13X19 print.
To interpret the following images, you MUST click on the image to see at full size. Captions are below the images. I inadvertantly left the lens at 18 mm. instead of the max. wide of 16. ISO was 100, focus was magnified manual at f4 (too hard to focus at f11, especially at the wide end - too much depth of field - remember that like my Nikon D800e and NOT like my previous Canon 5D2 and 3, live view focus (and in the case of the Nex-7 viewfinder focus too) is at stopped down aperture.
two thirds of the way out, 70 mm. f4
Extreme upper left corner at 18 mm. f4 and you can see that there is considerable difference even in this small crop - the lower right corner of the crop is already quite decent and is well out to the corner as you can see in the full image below.
It won't replace my Sigma 60 that is tack sharp wide open right to the corner for critical work, but given it's a zoom that isn't much bigger, covers almost 5X range and has image stabilization, I'm quite pleased with the lens and will be keeping it. Is it the best zoom ever? No. But at $1100 which is less than half the cost of my recently purchased (and damn good) Nikon 24-70, I think Zeiss got it right - noticeably better than Sony's kit zoom lenses for the Nex (18-55 or 16-50). As a walk around lens, it's plenty sharp where it matters and as a backup camera for serious work, f11 provides the resolution to make 16X24 prints of any subject.
Why did I purchase the 16-70 when the Alpha 7R has already been announced? Wouldn't it make more sense to use the newer camera and its lenses. The answer is size and versatility - I already have the 7, and it's sig. smaller than the 7R, and the lenses even smaller. I will now carry in my small cloth bag I like so much the 16-70, 10-18 and the Sigma 60 though I could see replacing that with the announced Zeiss 50 macro since I don't have really close performance with the current kit - but this is pretty low priority given this is my walk around kit.
Actually, I'm quite impressed with the close focus of the Zeiss 16-70 - no it's not for photographing bugs some prerelease images notwithstanding but at just over a foot at all focal lengths, it's not bad at all.
I don't think I could even get the Alpha 7R into my new camera case, and probably not the lenses either other than the 35. No, I think I have made the right decision. Now that I can access the PSAM 'dial' by centre press of the back dial, the lack of a real dial for same doesn't bother me nearly as much.
I need to explore custom menus more to see if I can move image stabilization somewhere more convenient - oh yes, and white balance and formatting cards.