When you're rolling prone in DayZ first person, your first person camera doesn't follow the head and rotate around, and seems to just stay straight. I don't know if this is intentional or not, but I think it looks kind of bad.
Also, when you are performing actions like drinking from ponds, wells, swimming, opening cans, cutting clothes, even when moving, It lets you look inside and behind your head, and feels very disconnected, from your character.