Summaron 35 2.8 is perfect match for M2. Absolutely perfect. The lens itself is amazing lens as well. Last one build in Germany like mechanical jewel.
Zeiss doesn't have real focusing tab, has 43mm filters and if you still scanning instead of printing, Zeiss bokeh is not as pleasing as Leica's lenses.
I would say Leica 35 lenses bokeh is neutral and draws into it. Zeiss 35mm bokeh is better not to look at. IMO.
I am sure you're gonna love that lens.
It doesn't have the Leica focus tab, but it similarly has a little knob around the focus ring.
I found this to be equally easy if not more comfortable than Leica's focus tab.
Actually my first 35 f2 Summicron had the tab and I didn't care for it. I'm more use to standard SLR type focusing rings and prefer one without a tab...just feels more "at home"..like 50 f2 DR lens.
Never tried the Zeiss, but imagine it would be all class. May I suggest the Voigtlander Nokton in 35mm, or their 35mm 2.5 Skopar? These are top lenses too, well priced and come out of the same factory as the Zeiss, just a different door
I got the Zeiss f2.8 lens today and it's a beauty-even a tad heaver than I though which I like but it's short like the Summicron. Maybe tomorrow if it's not still raining and the wind's not blowing 40 mph I can get out and try it out.