The main character, Teito Klein, isn't the best protagonist there is. He is an angsty kid talented in fighting, and his emoness is pretty much defines his character. Some of the other characters are portrayed better and more deeply (mainly thinking of Frau and Hakuren here) but in overall characters lack depth that would have been possible to portray in 26 episodes.
I haven't read the 07-Ghost manga, but I suspect that the makers have more or less struggled fitting the main points of the still continuing manga into a sense making entirety with a start and an ending. The ending of 07-Ghost is like a running into a wall. All of the main points of the series are left unsolved, it just... ends.
That's the bad stuff out of the way. Now, the good stuff.
The background art and the music in the series are very good: especially the guys who drew those backgrounds really knew what they were doing. Not only they go well with the story, but with each other as well. The feeling of watching 07-Ghost is the same when I was reading first Harry Potter book for the first time. The new, magical word and environemnt are beautiful and exiting, and somehow full of feeling: majestic hallways, the peaceful garden and and a calming fountain. It makes you wish 07-Ghost is a game, so you could just stroll around and explore the area by yourself.
So, what is needed to enjoy 07-Ghost? A pair of yaoi goggles, appreciation for pretty anime boys and a mind that can be swept away by magic, feelings and pretty things.
