Adapting third party lenses sounds great in theory. But in all reality, it pretty much sucks compared to having native glass. I bought the A7r knowing that there would be some losses with the gains.
After having attempted to use basically every piece of Canon glass I own on the Sony, I have found that the IQ is just not where I imagined it would be. However, when I mount the native 55mm, IQ is pretty darn good and I don't believe the lack of performance is any fault of the Canon glass.
My belief is that the issues are caused by having to add a piece of hardware (adapter) in between the body and the lens which leaves a lot of room for variance and play. The other issue is the way the sensor is set up in the A7r body. The EF lenses were simply not designed to work optimally in this scenario (distances, tolerances, etc). Whereas when I mount the Zeiss 55, I know that it was designed specifically for the FE mount bodies and microlenses which translates into much better IQ.
Prior to the A7r, I had already experienced issues with lens adaptation as I have used many M42 screw mount lenses on my Canon bodies. Many of those same issues have manifested themselves with the A7r + EF lens combos.
There may be a small segment of users out there that have gotten the perfectly crafted adapter that causes only minimal degradation, but my belief is that that segment is truly minority.
Furthermore, simply enabling AF and saying you've accomplished the ability to retain most features is not the same as actually making the lenses anywhere near as usable as in their native mounts. Don't be fooled for one second that you will be able to AF EF lenses on any of the Sony bodies in any real world situation where your subject is not lifeless.
IMO, the AF retention feature is a mere gimmick to get our attention and I'm certain less than a ball hair of a fraction of the people adapting EF lenses are bothering with it vs just manually focusing.
I suppose my point is that while it is great that Sony is encouraging the use of adapted glass, the actual reality of the experience is trash (on the average) which means they still need to start producing some of their own quality lenses in FE mount.