Canon received my 50L and my 5D3 on Tuesday. Today is Friday and my gear showed up this morning. Pretty fast service, I'd say! BTW, I am a Gold CPS member, which probably speeds things up.
The really great news is that the lens now focuses perfectly!!!!!!!!!!!!!!!!
I tested the center point and all four peripheral points and they are right on the money with no AFMA. I also checked for focus shift with aperture changes and did not find any at my usual six foot test distance. If I recall correctly, that was only a problem at minimum focus distance anyway, according to forum posts.
Sorry I can't comment on curvature of field, I don't have any brick walls handy!
The service note says that they only adjusted the lens, not the camera body. Apparently some optical assembly in the lens was still decentered after their first attempt at repair. They did clean the 5D3 body, including viewfinder and sensor, and they reset my custom functions to the defaults.
I am a very happy photographer right now!