I've often wondered if an EF 35-105 f/2.8L (IS) would be a popular lens. There are a lot of people who are upgrading from APS-C (and now will be moving from APS-H) to full frame; such a lens could give them the zoom range they're used to. Also, there are some applications for which 35mm at the wide end is probably enough, but would appreciate the extra 35mm on the long end (press photographers maybe?). A design starting at 35mm would probably not involve as many optical compromises as one starting at 24mm, so image quality would probably be improved. The lens would probably be a lot more manageable in size than the 24-105 f/2.8L (IS) that a lot of people seem to dream of.