My least favorite to write is Rose's enhanced body which includes a subtle but agonizing super strength/speed/perception/agility and a healing factor. Wolverine without the claws. It is my least favorite because of how much of a pain it is to remember to factor in when doing POV segments starring her, especially the perception bits. Heightened senses in general are a pain to include when writing from the point of view of a character who has them. I guess that counts for the vampires as well.