When I purchased the Nex7, I looked at both the Sony 16-50 and the Sony/Zeiss 16-80. On first blush I liked the 16-50 since it had a AF motor in the lens, which worked with the base Sony Alpha to E mount adapter. After using the lens, I found that the images were relatively soft, from F2.8 till about F6.3 after that they improved a good bit, but since I was really wanting the lens for the F2.8 to about F5.6 range, I took it back and tried another, and found about the same results. Again this was using the base Sony adapter. With manual focus and magnification, I could improve on this, but still could not get the images where I wanted them. The size of this lens was a bit large also, considerable larger than the 16-80 and even the E 18-200.
I then tired the 16-80 and really fell in love with this lens.. Someone already commented on the Zeiss contrast, but to me overall color and contrast both were better. The lens to me was excellent at 16mm to 50mm from F5.6 and up which was the main mm I was wanting. At 80mm the resolution to me gets even better and the lens at 80mm works as a very good macro also.
My only real issue was the fact that I lost AF with the base Sony lens adapter and manual focus was great (especially with the 11.7 mag) but there were times that I wold have preferred AF. (Video included)
I purchased a used Sony LA-EA2 and what a difference!. You pick up the Phase detect AF and have a tremendous amount of control over the AF points. ( I am still very impressed with everything Sony packed into the body of the Nex7). The LA-EA2 of course has a mirror (translucent) so there may be some light loss thus more noise. I have read some reviews of the A77 where the A77 seems to suffer a bit more with noise than the Nex7 and the reviewers have pointed to the mirror as possibly being the cause. The AF with the LA-EA2 is really impressive.
. Of course if needed, you can go back to MF and use peaking for fine focus adjustment.
As for CA, I just don't see it that much. If I do it's at 16mm to around 24mm but LR3 or LR4 take it out with no problem and seemingly no image loss. Still not sure I prefer the LR4 CA implementation for CA over LR3.
Image quality is really impressive on the 16-80, I can't state enough about that, you can get some very detailed images with it.
My results with the 16-50 were much less satisfactory, luckily I was able to work with a local dealer who allowed me to test both lenses. I say again the LA-EA2 makes the 16-80 come alive.
Paul