I'm with the folks who propose going large format for landscapes. Of course the larger neg and greater ability to render fine detail and subtle tonal differences is an attraction, but just think about being able to put the horizon where you want it and keeping tree trunks straight when you want them straight. Or what about not having the optical center be the center of the frame? For instance, you could shoot straight down a canyon, but the canyon doesn't have to be centered in the frame, if you've got left-right shifts.

If I want to shoot landscapes and don't want to carry a 4x5" or larger camera, I've got a medium format view camera too. SLR's are great for subjects that move, but for total compositional control over things that don't move too much, like landscapes, architecture, and still life, a view camera, in my opinion, is the best tool for the job.