In my opinion the Summarit is a very much underappreciated lens. Bokeh is outstanding and the debth of field is very small at 1.5 and 6 feet. Some have reported soft pics. Mine is reasonably sharp in a 12mm circle in the center of the field and acceptable in the corners. I just tested it against a mint lux first version and it was sharper, but individual s&les vary. Many are fogged internally and NEED to be cleaned before they work properly. Hold the lens against a dark field and shine a light through both ends and be sure it is clean. The coatings are very soft and need to be cleaned very carefully. At 2.8-4.0 they compare to the more modern glass. You need the proper lens shade at about $150. Mine wears a 41mm uv filter to protect the soft front, although I normally do not use filters.
If you want the old time Leica look, this will give it in spades. Full open portraits are georgous. I would not trade mine for any 50 lux, but then I have not seen the new one. I will warn you, it is a heavy lens with lots of brass and glass.