I have had, and will soon have again, the 35/2.5 Color Skopar in M39 mount. Adam found focusing it a bit fiddly because you need to use (in order to focus rapidly) the little knob on the lens. So did I, but left all other lenses at home for a week, using a Bessa R, and after a roll or two it became second nature.
The lens is indeed sharp and contrasty, and some might prefer otherwise. Alll lenses have differences, obviously, but if you want contrast and sharp, look no further. I did a portrait of a friend, a middle-aged woman - and of course this lens is not intended for that sort of work in general - and I had to use my old trick to tone it down, which consists of a darning hoop over which I've stretched a piece of panty hose. If it's a 20 second exposure with the enlarger, I give it the first 8 seconds straightaway, then interrupt the projected light from the enlarger and slowly move the hoop back and forth just under the lens. Softens things up and the subject doesn't get mad at you.
However, with architectural stuff, cars, motorcycles, etc., where you want sharp, the 35/2.5 is hard to beat.
