Just my take on double-stroke. I've never used a double-stroke Leica, but I have had a double-stroke camera - an Olympus Pen-F. And I hated the double-stroke. Because I'm so used to a single-stroke wind, I forgot almost every single time I wound on, and I only remembered when the shutter wouldn't fire. It was immensely frustrating. If I'd used it more I guess I might have started remembering, but I sold it.