I'm considering putting a 50mm Summicron on either a 5D or a 1DsII. I'm curious if there's anything I should know about or look for in this combination (e.g., works best with certain adapters, mirror issues, certain versions of the lens). I'm also curious what the going rate for the lens is these days.

Thanks,
Greg

Here's a fairly comprehensive thread on the 50 'Cron:

http://www.fredmiranda.com/forum/topic/717070

The 50/2 Summicron is an excellent lens. No concerns with mirror clearance on the 5D. I prefer the color rendition of the Leica over the Contax/Zeiss 50/1.4. The ROM version of the Summicron has a newer coating. The going rate will depend on version and condition - typically between $300 and $500.

Great lens. No worries on 5D (thus by definition a 1Dxxx - the 5D being the Canary In The Coal Mine of lens fitment). Great color, sharp, nice bokeh. Second opinion on colors vs Zeiss - which typically run cooler.

Yup, great lens! You will love it. I use mine all the time.

as to pricing, I recently sold an excellent 3-cam copy for $350 on ebay, I included a cheap EOS adaptor.

I own the older Summicron "made in Wetzlar" and the newer Canada made version. Booth are great. The canada version is a bit better at the edges at full open. At F2.8 both lenses act as same. The Wetzlar Version is more heavier and better build. Works great on 5DMKII.