There's also a Flickr group for vintage Summarit:
http://www.flickr.com/groups/71035126@N00/
Some of the images posted above are very nice, but my overall impression – from a web search when I considered buying one – was that the elderly Summarits are too soft & flare-y at their larger apertures. The flare seemed to wash out & flatten the image, with not enough differentiation in highlight tones. IMO this look is almost the opposite of what folks call 'Leica glow,' which refers to a more three-dimensional look & a more engaging or sometimes even romantic feeling.
When these lenses were new, many photographers opted for a 1.5 Zeiss, including Robert Frank & HCB (before he fell in love with his Summicron).
I didn't like the 1.5 Summarit's way of 'drawing,' & decided instead on a pre-aspherical Summilux (Type 2), which at large apertures renders light in a subtler way. With less veiling flare, the image doesn't look so flat. This is true for both the 35 & 50 pre-a Summiluxes, whose softness when wide open is due to spherical aberration rather than flare. ( It's actually this aberration that folks call 'glow.')
Another way to go would be the modern Sonnar C, optimized for 1.5 & used (when necessary) with a ND filter.
YMMV, also your tastes; but if any of this makes sense you might do better with a different lens.
Kirk