I have what I think is the C version, and it's a nice enough lens. If you get an APO for a very good price, it is worth going for, though, especially if you shoot colour slide film. I don't think the differences are that great once you go to black and white, especially if you use colour filters. On my 645 system, I have tested ULD (= APO) lenses next to their normal counterparts, and the ULD lenses are slightly sharper, but the difference is a lot less than what good technique vs bad technique makes.