I just got my my FD 20mm and 24mm f2.8 lenses.
I've
uploaded a bunch of test files if anyone is interested (warning 500mb+ file). Shots at all apertures working from f2.8 to f22. Focus on the tree trunk at f2.8 then not touched. I included a refocused shot at f11 to test for focus shift.
Ok first the lenses. The 24mm is tiny and very pleasant to use. With the FD flange distance being shorter than most SLR's, the lens mounted to the A7r is really small and comfortable. Manual focus is a dream. The 20mm is larger but still a very neat package on the Sony. The entire front of the lens rotates with focus which threw me somewhat, will be a pain for using a polariser, in fact as only the very rear of the lens stays stationary, bit annoying when trying to mount the lens. Other than that it's just as nice to focus.
I have the 24mm f2 lens on the way, going to test the two against each other and keep the one I prefer. To be honest I'm hoping it's better than the f2.8 version which although much better than the Pentax K 24mm I had, is still lacking somewhat IMO.