Elfen Lied was a gored letdown.
For simple pros and cons refer to the bottom.
Long reviews waste your time, so here's a short and sweet paragraph.
Elfen Lied has a pretty basic story that's nothing to die for. You don't feel desperate or compelled to protect anyone. Their situation isn't very dire as they just happen to stumble upon an alien with extreme powers and decide to take care of it instead of calling the cops. I call it an alien in order to preserve mystery. The plot was just too slow and unbearable. The art is extremely poor. You have to remember it's 2004 though. Pools of blood didn't have light detail drawn into them. It kind of felt like you go into the paint program, click a red color with the fill tool, and fill the circle of blood. All art shared this dry feeling. The sound quality in this anime is aweful. The nearly complete absence of music makes you feel like you are watching paint dry. The dialogue is lifeless and without the accompanying music you'll feel like your in a studio watching the recording process through glass. This contributed heavily to the characters being uninteresting and lifeless. The only characters who are noteworthy are the aliens and Bando because he's the only one who feels like he has a personality. The knife in the heart of this anime is the large lack of music. They put some effort into the intro song which occasionally surfaces but the gaps are just too wide. It felt like a complete lack of effort and neglected an entire element of anime. All in all, there are definitely worse anime but watching Elfen Lied was like watching paint dry. You should watch plenty other anime before this.
-Nearly nonexistent soundtrack.