First, after posting the above rant, I sent an inquiry to Zeiss, and I heard back from a rep in the old country within a few hours-- by about 6:00 a.m. my time. He explained that the NEX-7 autofocus system always hunts focus; it is designed that way. He ascribed my noticing it with the Touit to the louder DC motor in the lens for AF. Apparently Sony and Sigma use a motor type that is quieter. In the quiet of the early morning, I tested this with my Sigma 19mm, and the Zeiss rep was right. It too hunts focus constantly when the shutter button is not depressed. I hadn't noticed it before, because the motor in the Sigma lens is whisper quiet.
So we know now that the Zeiss AF motor is considerably noisier than the motors used in other lenses, and that this is a design feature. The link here will tell you about as much about the Zeiss Touit construction as you want to know:
http://www.lensrentals.com/blog/2013/06/really-getting-in-touit.
The Zeiss rep suggested that, if this behavior is too annoying, one should set the camera for MF and use the AF/MF button in either "press" or "toggle" mode to activate AF when desired. I will be playing around with that this weekend. I tried it briefly before work this a.m., and it seems workable, or about as workable as using the AF Lock button on Nikon D series cameras to autofocus, rather than the shutter button. I never got used to that, but then I didn't have a motive to.
I plan on trying to use the lens a lot this weekend, but so far, it seems to have the Zeiss IQ that I expected. If you scroll down on the lensrentals.com blog, one of the owners has a "first impression" review and MTF charts. If I can get used to the noise, the lens is a definite keeper.
