I have one monitor aligned horizontally and another aligned vertically, and I feel this works better than one large monitor or a monitor that swivels between the two alignments. I think part of this is because with two monitors, it's possible to rotate them relative to each other (ideally, I think, you would want a spherical / parabolic / hyperbolic monitor and this helps approximate that), but it might be that if I had hotkey shortcuts to easily throw windows where I wanted them on a single large monitor (like xmonad) I would be able to get most of the benefit.