It is *very* useful for candid street, as people assume you're just messing with your settings.
But it's good for landscape in two ways. One is when you're working very low, and don't have to lie on the ground to see what you're doing, usually with a wide angle. The other is a bit more lateral thinking, but if you don't need a tripod, it's surprising how often you can get better separation between picture elements by holding the camera over your head. I've had quite a few shots like that where without a folding screen I would have had to rely on trial and error. YMMV, of course. If you mainly shoot at head height or thereabouts, it won't matter very much.