While I'm no big vampire fan myself neither, they do have their place in DnD RPG's - with day and night mechanism in place that is - or did you forget about Bodhi in BG2 ?
I remember Bodhi very well indeed. My intention perhaps did not come across in my post; it was not about those creatures not having a place in D*D, it was more about the ramifications of the central character suddenly becoming a Vampire or Werewolf and how that would affect the story and how NPC react to you. It would seem to add rather a lot of work to make it fit the game world.
