A few things of note:
1. The video is very subdued - the music, the atmosphere, the art. It adds to a very tense, creepy atmosphere, which I think is what Aku no Hana is going for.
2. Other than that, there's very little to go on story-wise. It's intriguing but there's no real plot points jumping out at me.
3. No characters? I mean, slight shots of people but I don't see any actual figures emerge yet. For a series that is supposed to be rather unique in its animation with its use of rotoscoping, the lack of any real rotoscoping work in the PV is worrisome.
For those who have read the Aku no Hana/Flowers of Evil manga, what do you think?