I think that it probably depends on your definition of the word. Certainly, Spike loved Dru. I have little doubt that it was a strictly one way relationship, however. Granted, she took care of him after the Season 2 finale, but I can't help but wonder if she would have done so if Angelus had survived. Dru doesn't like to be alone. Given her mental state, I seriously doubt that she could survive very long without someone looking out for her, despite the fact that she seems to be doing so from one guest appearance to the next on the two shows. (O course, I feel he same way about Harmony, so I'm obviously missing something in the character of both wing nuts...I mean, vampires.
Angelus never loved anyone or anything, beyond the taste of hot, fresh blood, the younger and more innocent, the better. Angel, yes, but that might be cheating, since the possession of a soul seems to be what does it for him, and souls aren't standard vampire equipment.
Darla felt a certain amount of loyalty to the Master, and possessiveness of "her boy," but only to the point that it served her purposes. A choice between either one, and her own skin, and she would choose her skin, hands down.
Besides Spike, we had one example of a vampire who, apparently actually loved his mate (James?) so it obviously isn't totally beyond possibility for a vampire to actually feel love, it's obviously even more rare than straight talk from a politician.
