Interface and missing OVF/EVF is a hassle but the IQ is really good.
Thanks for your review, Dustin. It really has confirmed my decision to use the EOS M FOR WHAT IT IS.
I tried to revive my old FD lenses, especially the FD f/1.4 50mm S.S.C. - not as sharp as the Zeiss 1.4/55 but really o.k. I attached an image of a vineyard in Winningen near Koblenz, Germany. Made at f/2.8 and slightly postprocessed, sharpening is 4, Style is Faithful, set blackpoint, contrast +1 with DPP. The second image shows the center strip in full resolution.
The EOS M sensor has a spacial resolution which compares to a 50MPix FF sensor. I always have to keep that in mind if I look at images taken with a 40 yr old lens (!!!).