I don't have any experience with the 35mm hexanon, but the results by others that I've seen look nice.
I have the 35/2 summicron 4th version and at $600 I think that's a bargain if the glass is good and the mechanics are alright. There is nothing bad that one can say about this lens, IMO. It's small, sharp (enough for just about anybody), not too contrasty, and the out of focus rendering is truly pleasing and gives a nice 3D look.
From what I've seen, I wouldn't trade this lens for ANY other 35mm M-mount lens (ASPH or not)!