I enjoyed the anime very much. The first few episodes [in particular] had several moments of "what did I just watch??" where I had to hit the pause button, but much of the rest of the story was beautiful and tragic and disturbing. In my opinion, Lucy was a wonderfully complex character, lonely and in love, bitter to spiteful to misanthropic, and likeable at the same time. I wish the anime spent more time on her character than her alter ego Nyu (I haven't read the manga, so can't comment there). Kouta and Yuko were reasonable characters; Kouta was almost over the top with empathy, but in my opinion ultimately not too unbelievably-forgiving or such.
There's a lot of nudity. I guess an amount of it came off as more playful than objectivizing, e.g. Nyu being naked in unexpected situations than "let's pan the camera over this scantily clothed character in a sexualized pose", but there was still a lot of "fanservice". I thought the opening theme was artistic and curious—with Nyu and Kouta embracing manikins which seemed to take the place of one another—rather than "notorious", but it's certainly not PG-13.
The violence was definitely a thing. I suppose the copious amounts of blood didn't give me nausea; I guiltily admit to playing FEAR Combat in, well, a less happy part of my life. It didn't undermine the story for me, but I respect those who don't care to tolerate it.
All in all, I think the themes of love, acceptance, longing and sadness, mixed with spite and malevolent self-identification made the story tragic and powerful. Its aspect of monsters-vs-humans or sci-fi fantasy didn't seem as novel or outstanding (sinister research facility, anyone?), but I liked it as a tragic and contorted love story.