Yes, you read it right! Contax N with AF on a A7/Nex (through Fringer's adapter).
I've never been an early adopter, but I am a sucker for Zeiss lenses and Contax N lenses are legendary. I read in December that someone in China was demonstrating a Contax N AF E-mount adapter allegedly to be on the market in a month or so.
Thus, before buying my A7 (I have NEXes) I decided that I was going this way rather than Conurus+Metabones. I bought a 24-85 and a 70-300 at a reasonable price, and started waiting. It took more than six months, but now I am the proud (and mostly) happy owner of Fringer's adapter, and one of five or so outside of China.
Cheap it is not, at $595.00 shipped (plus custom). In fact, it costs more than my two lenses.
Is it worthwhile?
The two lenses I really like. The 24-85 covers most of my needs, and in spite of bad press, I like the 70-300 (which I use mostly at 300) very much. It's heavy, but balances very well, and I even succeeded in shooting hand-held at 300mm at 1/50 (#2, pure luck).
Aperture setting and EXIF work fine. The major reason to use Fringer rather than Kipon is, in addition to excellent quality (but Kipon is less than half the price), autofocus.
Autofocus is a bit quirky, but I am getting the knack to it. When it finds good contrast, it can be excellent even in rather low light (see #1, remote control from ipad), otherwise it misses, apparently more likely at infinity and large focal lengths (not very surprising). Sometimes it hunts, sometimes (rarely) it hangs.
More a problem of the camera than of the adapter, possibly. The adapter is version 1.0 though, and it might get better, although it is already quite good. AF speed is usually about 1-2 sec., adequate for my needs.