as mentioned the VC are good lenses, personally I used the 35 ultron for about a year on my M6... excellent quality I must say and unless you judge every picture with a 10x loupe I think it will serve you well.

It also depends a lot on your style of photography, I like OOF/Bokeh or whatever it's called, in this area the Ultron is rahter harsh (personal) and during the year of use I found myself shooring more and more a open apperatures and appreciating the OOF area as a counterpart to the actual image. I tested the 35mm asph summicron and the CZ 35mm 2.0 both for a couple of days and found that the Carl Zeiss meets my expectations so I bought that one and am pleased with it.