Back to this 11mm f/2 APS-C lens. Personally I think it'd be a KILLER lens for the format. One of the things you just can't do with APS-C ultra-wide angle thin depth of field photography because the lenses (like this one) just don't exist for it. It's far easier to do on full frame with a 28/1.8 or a fast (f/2) 20mm lens, but pretty much impossible on APS-C. You just can't get the same photos. It's not just the wideness and the speed, but also the typically better close focus capabilities of primes vs most zooms. If it could focus down to 20cm as well like the Nikon and Canon 14mm f/2.8 full-frame primes, it'd be awesome. I owned the Nikon 14/2.8 and you could get photos with that lens that you couldn't get with any of the zooms simply because the minimum focus was so much closer. Allows you to get some really unique photos. Lost a bit of its magic on a crop body, but that's what one of these puppies would be for.
As I recall, Nikon had a patent out a few years ago for something similar. I think it was a 9mm f/2.8 DX (APS-C) lens. I doubt that one or this EF-S 11mm f/2 would ever be built though. Would be a very special purpose and low volume lens, probably pretty expensive per unit, and most APS-C shooters would probably be confused and not really understand the point of it. I think they'd be better off building that aforementioned EF-S 35/1.8 to match Nikon. Those that did understand the point of something like this would probably be willing to spend the money on a full-frame camera and buying one of the 20 or 28mm lenses that are already out that can do basically the same thing.