I recently bought the 35 F 2.0 and was impressed with several characteristics. First for me was the fact that it plays nicely with Infra Red. Secondly the aperture ring is finally as close to perfect feel wise as I could ever hope for (something I'd never say about the aperture ring on my 14 - my favorite lens, optically) but I sent it back.
When taking a critical look at the extreme corners, the lens's IQ is extremely disapointing, and no matter how much I stoped it down, the extreme corners were badly smudged. I asked around and it would seem that such is par for the course for this lens. After sending the lens back and re-examining the images I think I noticed a patern that indicated that the close the focus the worse the extreme corners performed. At about ten feet or further, they were not nearly as bad. Has anyone else examined the corners closely and found them badly wanting?
With the current deals on the lens, I'm tempted to buy a second copy. It's a great lens in so many ways, save for close focus contrast (which I didn't find, but read about) and those awful corners on my copy. If I didn't want the lens for Infra Red photography landscapes, I'd simply live with it. It really is a bit of a nit-pick, and perhaps I can crop and live with it as a 58mm lens? On the fence right now.