EF-S on FF sounds cheap and not very smart APS-H is a better reason for such discussion.
IMHO, Canon should have made 1D bodies compatible with EF-S lenses, because now they are selling a pro body that can't shoot UWA with OEM lenses. 14mm x1.3 ~ 18mm, 16mm x1.3 ~ 21mm.
Big mistake, Canon.
The 1D bodies weren't made for shooting UWA; they're for shooting action/wildlife at tele and super-telephoto focal lengths, hence the 1.3x crop and higher frame rates. A pro or serious amateur who needs to shoot UWA, is going to use one of the full frame (1Ds or 5D) bodies.
That may be true from Canons perspective but after getting addicted to the 1D interface I don't want to go back to a small body and can't afford/justify a 1DS so we run a pair of 1D4s. I'm an (arguably) serious amateur and sometimes I like to shoot wide and theres the rub.
Well, life is about making compromises.
If you really want to shoot landscapes, then you can't go wrong with the 5D (either version). A used 5D classic will run you about a grand. Personally, I love the "Custom" modes on the 5D Mark II: configure all the settings any way you want and save it. Then, just turn the dial to that setting and you're ready to shoot!
Another option is the new EF 8-15mm f/4.0L fisheye. You'd have to use software to "de-fish" it and you'd lose a bit of the frame in the process, but it would still be wider than any other EF lens.
Finally, you could use the original EF 15mm f/2.8 fisheye and not "de-fish" it. Here's a link to a guy I found on fredmiranda.com who uses fisheyes on all 3 formats: full frame, 1.3x and 1.6x. On the crop bodies, the 15mm isn't too "fishy" looking, so it might be a usable compromise.http://www.pbase.com/dbehrens/15fe