I thought it was tres kawaii! And yes, it does differ greatly from the manga. :( But I think that's a good thing. The manga was great, but it wasn't nearly as serious as the anime was. In the anime, there's a lot more drama. ^_~
And don't be dissing Kamui! She was just doing her job! Sure, she was a bit pig-headed about it, but she came around, lol. I'd have to say that the only characters I didn't like were those hacker kids that messed everything up... except for the girl at the end. I just felt sorry for her. :(
And my favorite character was definitely Komiyama-kun! XD I just broke up every time I heard that ridiculous laugh of his!