I have one for my Nikons. A great lens which I only take off to put on a Nikon f/2.8 20mm to 35mm zoom when 28mm will not do it. I have used it to produce negatives that I enlarged to 24"x36" for framing.
I wouldn't use it for anything but casual snapshots. A couple of my buddies have and use it, and I haven't been impressed with anything from it. One of them gave his away.