I'm more of a wide angle shooter and I'm currently shooting a 28mm FD that I like. I've thought recently about going wider but am wondering how useful something like a 20mm would be as a cityscape and landscape shooter. I'm wondering if it's a focal length that's just occasionally useful or is it something that you reach for often enough to justify it. Obviously it depends on the subject matter at hand, and your own preferences (likes), but where does it wind up with you? Is it worthwhile out to 11x14?