I tried a few shots while shooting the dancer last week. I don't find them real sharp wide open and up close but love the look once you stop down to f4. The lens has a great look to it. This was shot at f2. It's a jpeg right out of the camera, nothing done to it.I also took the lens to Haiti for my shoot there. Stopped down it makes a nice landscape lens, although I think the Planar 50 f2 would be better in this situation.
If you're looking for a 50mm lens for your rangefinder, I have the 50mm Planar in stock right now. The Sonnar is on backorder.
My retail store for traditional photo supplies is www.bigcameraworkshops.com
My retail store for rangefinder gear, including Ziess lenses, cases and film is www.rangefinderstore.com