I'd like to start off by saying that this was a new experience for me. This is the first anime I have watched in full, and I was even inspired read the manga (another first for me). However, I thoroughly enjoyed this series as a whole. I did think that some of the humor was slightly cheesy and run into the ground, but most of it was alright. I think that the character development was excellent for most characters, especially in Karin's case. Karin Aoi starts off as a naive girl with a fiery personality, but as she is forced to make tough decisions, Karin becomes a very mature young woman.
There are a few things that ruin this series for me, and the front runner of those is the ending...Now, I won't ruin it for anyone, but because of the ending, I'd love to meet the writer of this series, shake his hand, and punch him in the face. The ending ruined the entire series (for me anyways). Instead of walking away having enjoyed a great story, I am just left here wondering what possessed Katsura to write this ending. It's just heart-wrenching and depressing.
You may be wondering by now why this got a 7 from me by now, after reading my rant about the awful ending. I gave it a 7 because of the great character development, the decent story, the great artwork an animation, and how memorable it was. I would recommend this series (and the manga) to almost anyone, considering the fact that I'm not even into this kind of stuff and I enjoyed it.
Also, a message to Katsura and the other creators that won't read this: If you were to pick this project back up for a spin off series for Karin, you'd have a gold mine. She was a fan-favorite from what I've heard, and I can guarantee that it would be a hit, so long as you don't screw it up again. Please pick it back up and give us an ending that doesn't SUCK.