My sample came well beaten up, with the filter ring bented and the focus ring locked.
I repaired it by myself with a couple of hammer blows.
Now it works like a charm.
Unbelievably small and compact for a SLR lens it is, like every almost other normal lens, a wonderful performer. Even if, for compactness sake, it lose something compared to other normals.
Your mileage may vary, but I find the 40mm focal lens almost perfect. It is wide enough, and long enough, that you may go everywere with just one lens on the camera, for casual shooting, and cover pretty every photographic opportunity you may find during your rounds. Really a one lens band!
Rating: 
on film
Rating: 
on digital (full frame and Dx)
I learned a lot from this post, much appreciated! 🙂