I bought this lens to have a fixed, light lens to use with my digital EOS 10D (due to 1.6 crop factor it has the same viewing angle than a 45 mm lens, in the "standard" range). I use it in "keep it simple" photographic sessions.
Resolution and overall image quality are quite decent; but it has one main drawback: vigneting is non-negligible at f/2.8, even inside the digital cropped frame (so I can't guess how bad could it be in a full 35 mm frame). At f/4 it becomes usable. I've done a very informal comparison with Canon EF 17-40 L and both lenses give comparable results at f/4.
Design is old, but effective; it has a depth of field scale. I'd like it to have a more silent focus engine, or a somewhat more robust build, but it does its job.