Based on my experience from 90elmarit on M9, a f2.8 lens. I still have hard time to nail focus especially at distance, thus I put 80lux in front of 75lux on my book. It can be more useful with future leica M or DSLR body. Though, focus 75lux might not be a concern with future M.
Paul, nice samples from 90AA, you never short of fancy lens. This is might be the only case that R is more expensive than M with overlap of both.
I know it has outstanding sharpness and colors from your sample, but I am not very convinced with Its Bokeh. But i know Bokeh is very personal.