I too would rate the Summitar highly. I have around fifteen 50mm lenses and I'd rate my Summitar my 2nd favourite. First would be my 50mm Summilux-M ASPH, which is a completely different beast. The 50mm f/3.5 Elmar would be a close third.
The Summitar renders beautifully. At large apertures, the image is sufficiently sharp and gives very pleasing portraits. Stopped down, contrast improves dramatically. It's like having two lenses in one. The collapsible Summicron is gives sharper images throughout the frame but the Summitar is gives sharper images in the centre.
The only thing that I do not like about the Summitar is the non-standard filter thread. One is basically limited to old Leitz filters that usually not in great shape. I highly recommend the Summitar-to-e39 filter adapter from S.K. Grimes. This adapter allows you to use very common e39 filters. Leica made such an adapter too but it is rare and usually more expensive than the lens itself.
Also, the S.K. Grimes hood made of the later Leitz 12585 hood fit more securely. The original barn-door hood for the Summitar is huge (and ugly). One can also use very economical e39 hoods from the likes of Heavystar. The lens does flare easily... With this lens, it should actually be called
flair.
Madelena by
~ Nando ~, on Flickr
For 35mm, I think that no lens is finer than 35mm f/2.8 Summaron. I have the M-mount version with the goggles for the M3 but an screw-mount version is available. It is truly one of Leica's masterpiece lenses. It is an extremely high-resolving lens. Corner-to-corner at every aperture! Yet it still gives a classic look. Absolutely magical with today's finely grained films. Also gives wonderful tones traditional B&W film.
P is for Porsche by
~ Nando ~, on Flickr