I'll begin with the good stuff:
The art is very good, and the author clearly knows how to draw attractive people.
Also, it's quite sensual. (Even for my not-really-liking-yuri tastes.)
And now, the bad stuff:
[ul]
[li] It is not romantic. The relationships between the girls seem mainly based on lust, not love. [/li]
[li] It is not "realistic". It takes place in that usual parallel universe where straight human females have gone extinct. [/li]
[li] It is not "realistic", pt.2: If I don't find ordinary harems realistic, yuri harems don't really have much hope. [/li]
[li] It is not character-driven: I don't think there was any character development at all. [/li]
[/ul]
(The word "realistic" is in quotes because, well, vampires don't exist in reality either. But the existence of vampires was something that was established well enough; the non-existence of straight girls was not.)
Here's what it gets a pass on: The humour, and male representation. Both are quite fine, but sort of unimpressive.
All in all, this is based on two genres (yuri and harem) that I don't really like unless they're done really well... and here they aren't. The reason I didn't drop it earlier is because neither of those genres was apparent from the get-go, so it took me a while to notice.