Maybe it's just my particular DR. I have failed to create busy backgrounds with it, even though I tried:
And it has the typical classic Leica shallow DOF, less than you expect.
I have however created the occasional double lines and asymmetric background circles with every Sonnar that I tried, except the new ZM version. The strength of most 50mm Sonnars is center emphasis, compactness and flare resistance, not bokeh.
Bokeh is of course very personal, and my taste has changed over the years. I like lenses were the OOF behavior attracts/leads to the subject in focus. Not when the viewer gets attracted to funky background circles. If your photo attracts the viewer to the background, there is something wrong with it, IMO: it is called background for a reason
🙂 And, while I used to shoot them myself, I find photos with sun-lit leaves in the background (demonstrating "good bokeh") now quite meaningless. They do not represent a typical use scenario, unless 90% of your photos are of trunks, branches and leaves. Even optically, they mostly say something about coma of a lens wide open, not about typical in-use OOF and its transition.
The faster classic Leica/Mandler lenses, at less than 2m distance, all have veiling flare, and performance really gets quite bad when getting close. While one of the Summicron strength is close up performance (as often needed for portraits), 50mm pre-asph Noctilux and Summilux were optimized for journalistic application, and are, very close, quite soft and flairy, not too useful, unless you only show web images, or like the Leica "glow".
My 2 cents
🙂
Roland.