I've never worn them much because pretty much all of my shirts end at the top of my hip, and I don't feel comfortable not wearing a long shirt with leggings. Recently, though, I got a lot of long shirts so I'm planning on wearing leggings more often. They're super comfortable and are great for this moderate fall weather my area has been having.
Of course leggings are sexy if you're wearing a shirt that doesn't cover your butt and you have a nice body. Leggings are a thin strip of material that cling to you like a glove. With a long shirt, though, they're about as sexy as any other pants.