Hmmm. One of the things I liked about FK was the way they strictly limited the vamped out look—basically to fangs and (sometimes) eye colour. I dare say their motive was financial. Still, humanocentric of me or not, I think it's easier to see the characters sympathetically if they don't look stereotypically "monstrous". Or, to put it another way, it's too easy to mentally split the character into good and evil sides (e.g. Angel vs Angelus) if there's a major difference in appearance.