This anime is near perfect. Despite having only 13 (add 1 more if you include the OVA) episodes in the series as of now, Elfen Lied surpasses all expectations in all aspects. The art animation is beautiful and a pleasure to look at. The story itself is brilliant. A very violent and emotional story about a girl, Lucy, and her life and place in a big conspiracy about human evolution. Honestly, I'm not into violent movies as they usually ruin a movie (because there is just too much blood/gore), but this series is an exception. The violence accurately depicts the mood and tension of the series. Elfen Lied's storyline is rather deep and gripping. Probably on par, if not better, than Square's FF7 plot line. And I love FF7. Elfen Lied is just that good. The music also "clicked" perfectly with everything. The OP "Lilium" is a beautiful piece that I find myself thinking about a lot, along with the characters and the story. Highly recommended watch to everyone, anime fans or not. Take note however, that this anime is brutally violent but still manages a perfect blend of everything else.
One more thing... I haven't seen the English voice overs. I have only seen the Japanese version with English subtitles. Well I hope that doesn't ruin the series... well it's kinda hard to with this series being so great and all...