The Vampire class is the class that all DM's are going to hate, and at least one person at your table is always going to want to play.
I don't see the appeal myself, but I dislike Changelings, Dragonborn, Shardminds, Tieflings and all the other monsters already. The vampire is certainly not any worse than any of those oddball options if you like your D&D in a Tolkienish flavour like I do.
I also have to admit that a new class is also the best way to add a template onto an existing player character race. As well, it isn't any more bizarre than playing a revenant, and I've seen revenant builds that are designed to look and act like vampires already.