Further to the discussion of the DA 10-17mm above, and for my own interest, I took photos of the same scene at 10mm and 17mm today to show the results at the fisheye-end and the less distorted end.
Personally, I don't use the lens much for landscapes. My super-resolving, less-distorted K28/3.5 is great for that (including stitches). I find the DA 10-17mm more useful as an urban walk-around in narrow European streets; for a "fun fishy" view; and occasional family/sports/buildings shots at f17. So here is quite a typical scene for my lens, where you can see the range of view and distortions.
Mrs Utak calls this lens the "fishbowl", and has no love for the distortions on the left, so it's not for everyone!