I flip to it when the camera's trapped in a corner and I don't want to see my toon's head obscuring half the view, or if I want to take screenshots. It's nice traveling in first person with the UI hidden, but there are too many things to keep track of in normal play to really keep it up. I say that as someone who used to play EverQuest in first person 24/7. FFXIV just isn't made for first person.