My brief comment here is on the Leica Summicron (f/2.0) 90mm lens. I had this lens renovated by Leica in NJ in August, 2013.
My preliminary observation on this lens is that it is remarkable. My best evidence is from a chum who put this lens on his Sony A7r. this remarkable snapshot shows the beautiful quality of the bokeh at f/2.0.
And here is a 100% crop in the upper-left corner.
(Again, I did NOT take these pictures, nor is it my camera. But it is my lens.)