Well, 58 on 4x5 or 617 is pretty freaking wide already. It would be a real challenge to take a landscape with that and not have a greatly diminished sense of vertical scale. I am not saying it can't be done, I am saying that one has to really pay attention to how foreground and background elements interact, and vanishing-point issues can be so prominent as to dominate the whole composition. I think I am agree with Jim's point that "wide open expanse" can be alluring to the photographer but not necessarily effective in the photograph.

Anyway, let's set focal length / FOV aside for a minute and see if we agree that with pano images a major challenge is to build front-to-back depth. The aspect ratio tends to emphasize horizontal compression. (assuming we're talking about landscape-orientation for now) I am merely asserting that this is a bigger challenge (for me) than figuring out what to put where in the frame...

Of course, there are vertical panos too, which can be gorgeous. I am remembering some of Geir Jordahl's photographs in his recent book.

By the way a pretty interesting gallery of panos may be found on the fotoman site. It was while perusing those that I started to think a bit more about what makes a pano effective and deciding whether I can do it.