I think it very much depends on the fiction in which vampires are incorporeated. The vampires in Buffy for example are pretty awful, at least on their own, but they fit the fiction, and together with all the rest they fit in, and they become better than they would be on their own. The vampires in WoD work pretty well on their own, but with all the other supernatural creatures in the world, they kind of fall flat. The vampires in the Warhammer universe are awesome, but sadly neglected, and not used to their full potential.
It also depends on the purpose of the story, and the role vampires are supposed to play. If vampires are supposed to be the protagonists (though not necessarily the main characters) then they still have to be somewhat human, relatable. They have to be able to control (or at least direct) their impulses, and be able to interact with humans. On the other hand, if the vampire is an antagonist (I really hope people know what the words really mean), wether as a villain, monster, or pet, on the other hand, more freedom is available. I personally like the image of the vampire as a deformed beast, like in some older legends, gone mad, being just a savage animal hungering for the blood of humans, no ability to speak, or reason, but highly cunning, supernatural strength and resilience, and with a host of other instinctual abilities, with an appearance similar to the vamps in Heroes 3, but even more so.
Ghouled, or embraced animals are pretty cool too, especially animals you don't really expect. Not wolves or bats, but snakes, cats, panthers, birds.
I really don't like the sciency vampires of Blade, Underworld or Ultraviolet (or the Initiative). I can understand the want to understand how it works, but the point of vampires is that they don't. I don't have anything against attempts at explaining it, just not when it works, or a fiction tries to explain in technical terms how vampires work, or throw uv-lights at them or something. It's the life-giving properties of the sun, the importance it has on culture, life and development, it's spiritual importance that damages them. Not uv-radiation. It's not a virus or poison in their fangs that turn others, it's a curse, passed along. Their strength, speed and abilities aren't measurable, or possible to explain, they are supernatural, mythological creatures for a reason, and should be allowed to remain so (this goes for all fictions). That particular part is handled very nicely in Cyberpunk, where belief is what shapes a vampire, and determines it's weaknesses. At the moment of their creation, their beliefs of what kills a vampire will shape them, and will be the only thing able to kill them, and keep them dead, because when those conditions are met they will surrender, give up, and they will THINK that they're supposed to die, subconsciously killing themselves instead.
