I have both the early version and the 2016 later version and I have not noticed any differences on full-frame digital Ms. Some say they prefer the rendering of the earlier version, but I don't see it. The later lens is said to be more suited to digital sensors than the earlier lens, and again I'm oblivious.
I've used the 28 Summicron a lot on the Minolta CLE because the lovely 28mm framelines in its viewfinder make viewing a real pleasure. Same for the Leica M8, where it seems like a natural choice, and mimics about 40mm focal length.
The very thin sensor cover of the M8 is well-known to pass quite a lot of infrared, affecting color rendering not just of black artificial fabrics but also other things like green foliage. And later full-frame M sensors have slightly thicker cover glass but still pass enough infrared to be noticed, so I continue to use UV/IR cut filters routinely. OK, foundation laid...
The larger full-frame digital-M sensors record cyan tinting in the corners with the 28mm Summicron with the cut filter mounted. This can be avoided by not using the cut filter, but I'm "allergic" to any IR contamination in my photos! So I routinely use CornerFix software to correct the corner tinting. This is more of an issue with such wider lenses.
This lens is a gem. Compact, fast, sharp, nice rendering.
Search the RFF Gallery for images with this lens... See "Gallery Search" on the Gallery menubar, pick the lens from the list and enjoy the trip!