Researching into AF adapters for A7R, here are the apparent choices:
The ones without AF are pretty cheap, but there are quite a few that preserve AF, IS. From researching these in an effort to find a reliable one, the user experience seems to be that AF is similarly slow via all of them, and each has different electronics/software leading to one working better with some lenses while another adapter may work better with other lenses (Canon or third party).
Metabones Mk III adapter seems to be the most popular with most user reviews but also the most expensive at $400. It does not work with all lenses at all, however:
"Only Canon-branded lenses introduced in or after 2006 are officially supported. Autofocus may be disabled for older Canon lenses and most third-party lenses, including most Sigma, Tamron and Tokina lenses and all Contax N lenses modified by Conurus."http://www.metabones.com/products/details/MB-EF-E-BM3
A Youtube video showing the AF speed with Metabones adapter.
My next choice would be RJ Electronics one which is cheaper with good user reviews available. Some claim it gives sharper results than Metabones III (how?) and works with older Canon lenses unlike Metabones. RJ admits it does not work well with Sigma lenses. I read one user who said that Canon 100L Macro did NOT AF when focus limiter was set to 0.3-0.5m (Macro range) but AF was fine at other settings including "Full."http://www.rjcamera.com/ocart/index.php?route=product/product&product_id=81
This Viltrox zinc-alloy one seems okay as well. I have a Viltrox Canon EF to M adapter which works OK though a bit loose on camera end. One can find a couple of user reviews on line, so at least you know it "works."
I found a video on Youtube that shows AF speed with Viltrox adapter and Canon 17-40L.
This Chinese one is claimed to be made from brass with AF intact. Unfortunately, no user reviews can be found.http://www.ebay.com/itm/Canon-EF-Mount-Lens-Mount-Auto-Focus-Adapter-for-Sony-NEX-7-a7-a7R-5N-5R-3N-/271342856622?pt=US_Lens_Adapters_Mounts_Tubes&hash=item3f2d4b69ae
This "King" adapter looks interesting as well but again no reviews can be found.http://www.ebay.com/itm/201023366624?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
TechArt version II adapter.
It's thought TechArt and RJ adapters may be from same oem, sharing the black finish on the camera side and also sharing the inability to recognize focus-limiter on Canon lenses. It's selling a little cheaper than RJ.http://www.ebay.com/itm/Techart-VER-2-Auto-Focus-smart-adapter-for-Canon-EOS-EF-to-Sony-NEX-7-6-5-a7-a7r-/251460489246?pt=US_Lens_Adapters_Mounts_Tubes&hash=item3a8c36901e
Deo-Tech Falcon adapter
This one also looks to be the same adapter as RJ and TechArthttp://www.deo-tech.com/
Upon further research, some users including Fred Miranda are reporting that RJ/TechArt/Deo-Tech adapters are softer with more CA in the edges compared to Metabones III.