Painful, isn't it? For example, I really want the Pentax DA 21mm Ltd, as it is tiny and is a perfect match for my K100D. Or, I could spend less and get a proper 35mm for my Nikon (film) and still use it if/when going FF in the future. Decisions decisions... Getting the 35mm means walkabout camera is film, so no flexibility with ISO etc. Getting the 21mm means smaller package, more likely to use and ISO flexibility.