If we will only talk about the anime and not the manga then this anime is actually good.
Story: 8/10
The plot is good and interesting. But that was all there is to it. The whole series were mostly about Yuki and Zero's everyday life as night guard in their academy (to make sure that the Vampire students will not do anything bad to human students). It mostly focused on Zero's suffering and struggle.
Art: 8/10
The art is nice. Although sometimes the characters eyes are too big and they look old for their age.
Sound: 8/10
The opening and ending song suited well for this anime. It sound so bloody,dark and mysterious.
The sound effects are also good. Especially whenever Zero pull the trigger of his gun.
Characters: 8/10
Yuki: She acted strong whenever she was with Zero. But she became weak,easily manipulated and act like a puppet whenever she is with Kaname.
Zero: I don't know whether the mangaka created him while thinking of someone she hated. Because she really gave this guy nothing but pain and suffering.
Kaname: Someone who's intention is something you will get curious about, only to get disappointed. The reasons behind his actions are too shallow.
Overall: 8/10
It's good although some things doesn't make sense.
The vampires have interesting powers but never really used them.