I like Cassie. I do. But I feel like, towards the end, it became way too clear that KAA was, as she herself has admitted to doing, using Cassie as a mouthpiece for her own views on war, ethical treatment of humans, animal rights, environmental issues, and all that jazz. I feel like, towards the last arc, Cassie-as-a-moral-statement outshone Cassie-as-a-character, and suddenly, everything Cassie did was exactly right! Hey, that wasn't treacherous, to give the Yeerks the Escafil! Because Cassie knew that the Taxxons would revolt as a result of not getting the morphing power because, despite having never spoken to a Taxxon, interacted with a Taxxon, morphed a Taxxon or spent significant time talking about Taxxons, Cassie knew exactly what a cannibalistic alien worm would do in that very specific situation.
She knew.
Cassie interested me. She's not my favorite, not my least favorite; I like her. I think she made her compromises and her deals-with-the-devil, very quietly, along the way, and then struggled to forget them. I think, beginning to end, she wanted nothing more than to not lose the side of herself that her parents were proud of, her friends admired; the parts of herself that she, herself, liked- and, in trying to stay on the lighter side of that line, she did some things that many peeps think of as stupid, and, ironically, as morally suspect. And I think she came very close to losing that side of herself, and it scared her, and it made her interesting to me. Trying to hold on to morals in a war, where someone will die no matter what you do... it's an interesting conundrum imo.
I hated it when she was never, never wrong. And the whole MM4 "You're, like, the heart of the universe!" thing. She gets too many superpowers. xD