I did not read the manga so the review is based entirely upon the anime. I don't really describe what happens in the series and spoils are from none to very little. Look at the description if you wish to know what the anime is fully about.
Story-7: Wow, vampires that have been hiding among us for centuries! I've never heard of anything like that before! That was sarcasm, if it wasn't obvious enough. Honestly though, yes it is overused and this anime doesn't pull it off as well as many other books or movies. But it doesn't have to. What I find very well done is how they justify their ability to hide and survive in the time they have been oblivious to common humans. In the beginning the story is very poorly developed but everything starts adding up around the latter half of the series. Don't give it up too fast.
Art-8: Everyone loves a naked 10 year old right? But seriously, it's not as bad as everyone is making it out to be. Although there are times when where they directly focus on her sexuality as a child, these are usually short and aren't that bad. So people should just take a chill pill. The animation moves in a way that Bakemonogatari does (yes I'm using it as an example, but in a good way) in that random motions and images are presented and there is a lot of emphasis on speech. Overall, expect fight scenes to have a dark undertone and blood is apparent when bodies are being cut in half. But that's just being realistic isn't it?
Sound-6: The background music doesn't stand out. The voice actors also don't really make themselves apparent. I do, however, enjoy the sounds that represent pain. They are far more realistic than many other animes and have almost a surreal quality.
Character-8: The characters are bland and some come in and out of existence way too suddenly. You're left with a "Who the hell was that guy?" kind of feeling a lot of the time. Despite this the Vampire princess is actually a very complex person and it stands to reason that most of the character development revolves around her. The rest of the characters are basically just there although some things do get explained during the last couple of episodes. I don't see enough character development based off of Akira but i still like his interactions with the rest of the characters.
Enjoyment-9: I actually enjoyed this series very much. Although the whole series wasn't "excellent," it was still a good watch. There are some very unpredictable moments which surprised me when I first read the reviews, stating that it is completely unoriginal. Oh and the princess' true form is sexy as hell, even though it uses a light effect instead of skin for representation.
Overall-8: If it's taken for what it is it can be very enjoyable. I'll probably get lots of haters for this who try to only see the things wrong the with the anime and people who just can't sit back and enjoy. Sigh...well this is long enough already so I'll just end with saying if you like it, awesome, if you don't like it, that's cool, and if you've never seen it, you should give it a try.