These sorts of discussions seem to me to always be so subjective - usually dependent on what the particular member owns right now, and possibly what they may be selling in the future.
In the same spirit(!) I'll say that I've owned 2 different pre-asph 35mm Summiluxes - both of them in really nice shape, but both of which I sold because I felt when used wide open they were simply too soft and 'glowing' (and even though people call it 'Leica glow' sometimes it's just horrible indefinition and coma - and I'm saying this as someone who really likes low-contrast, slightly unsharp, 'old-fashioned' lenses!) Having said that, every now and then I'm tempted to get one again...
Now I own both a V4 Summicron 35 and the Summicron-C 40mm that someone else mentioned in this ancient thread. When I first bought the v4, the plastic component that gives the positive 'click stops' for apertures had worn out - but I had the whole lens CLA'ed and collimated and this part was changed, and now the lens focuses perfectly and feels really solid and beautiful. For me, it has just the right balance of (ahem) 'Leica glow' and sharpness - a beautiful, subtle look.
Some people call it over-valued, but I don't think you'll find many owners of the lens who feel that way about it. Worth every penny imho.
The Summicron-C is a
vastly undervalued lens. The look is indistinguishable from the V4 Summicron - it has a lovely, classic creamy subtlety to the images - and the build quality might maybe even be a touch better(?) Lots of people have now written about this lens as Leica's "best-kept secret" - in fact this has been repeated so often the opposite is now the case. But for some reason these little beauties still sell for (relative) peanuts. I should know - I was recently trying to sell an entire beautiful CL kit and failed miserably even at a price that this lens deserves on its own.
All my subjective opinion of course.