How do you feel about being able to see someone's underwear through their skirt/pants/whatever? How do you feel about being able to see their underwear above the waistband of their pants?
My male coworker thought it was really hot that he could see this girl's underwear through her see-through skirt. I think that's a total turn-off. The only time I want to see someone's underwear is when they're not wearing clothes over them ;p