Roger,
I have enjoyed your review,and have learnt some new things from it. As a subscriber to your site, and without trying to wax lyrical about it, I can say it is the most useful site for learning how to enjoy high level amateur photography. I just wish there were a specific corner for the digital darkroom users, but this is my personal point of view.
However, as much as you have given your high preference for the C Sonnar, I believe you have failed to illustrate its main photographic strength and selling point: it is THE portrait lens par excellence.
The way it combines softness with high contrast ( at least above f2.0) and resolution with a buttery in and out of focus, which is also very ABRUPT, even at f2.8, makes it an ideal tool for a half body human subjects rendering. I like it most combined with a chromogenic film for female subjects, and with silver B&W film for male portraits. I enclose some shots (mostly taken at f2.8) to illustrate my point - unfortunately, my best portraits will not be included, because they are private.
http://www.flickr.com/photo_zoom.gne?id=1019892254&size=l
http://www.flickr.com/photo_zoom.gne?id=2080930169&size=l
http://www.flickr.com/photo_zoom.gne?id=870520088&size=l
http://www.flickr.com/photo_zoom.gne?id=1019894492&size=l
http://www.flickr.com/photo_zoom.gne?id=2081717026&size=l
http://www.flickr.com/photo_zoom.gne?id=1019034753&size=l
http://www.flickr.com/photo_zoom.gne?id=1434532050&size=l
I find, at f5.6 this lens becomes more of an all purpose tool, but with still its unique combination of resolution and softness which works well both with human subjects and not.
http://www.flickr.com/photo_zoom.gne?id=1809723689&size=l
http://www.flickr.com/photo_zoom.gne?id=709096134&size=l
http://www.flickr.com/photo_zoom.gne?id=2073880501&size=l
Moreover, it has its niche application in the shots that draw heavily on the bokeh:
http://www.flickr.com/photo_zoom.gne?id=866800228&size=l
http://www.flickr.com/photo_zoom.gne?id=1042614305&size=l
http://www.flickr.com/photo_zoom.gne?id=1971721096&size=l
http://www.flickr.com/photo_zoom.gne?id=1581934608&size=l
Personally, I think this lens is one of the most interesting photographic tools I own. I have actually bought a second copy of it, this one modified by Zeiss to focus correctly wide open, and I intend to do some tests as time permits, in order to make up my mind which version suits better my needs. I will share the results with you, obviously.
It also wouldn't be such a bad idea, to go back to dr Nasse, and give him some feedback, in order to contribute to a better fine tuning of this product, and above all, to convince him, their marketing has been quite negligent about it. I have read your comments about the degree of influence an "official tester" can have on Zeiss decisions, and it doesn't look like it is a lot...
However, I think even if Zeiss draws most of their income from other fields, the legend of the Zeiss lenses in photography, is certainly one of the cheapest forms of deserved publicity they can create ( while making great tools for demanding photographers).
Looking at the ZM line, I actually wonder, how it is possible that people continue buying Leica lenses at such inflated prices?
Outside of some specialist high speed lenses, which Zeiss has not produced in the ZM line (yet), there is no doubt for me that Zeiss delivers comparable optical and build quality+superior flare control, at 1/3rd of the price and with a drawing and 3d effect (yes, I insist on this) which is much more pleasing in final images.
I think this Leica preference is simply based on a tradition of a long line of first rate products, AND on a kind of mythical status, earned by clever marketing. Maybe Zeiss should have sold the C Sonnar at USD 4.000 price tag, showing us superb shots (by a noted photographer) of a George Clooney or Angelina Jolie ??? I am sure people would have been dumping their ASPH Summiluxes in favour of the C Sonnars, to be able to take shots like that... ;-).