While I liked the idea of the CATs and I enjoyed Carina's role in this episode, there were some things that were major flaws in this episode. First, I feel obliged to comment on Sarah and Zondra's "sparring session" - it was unrealistic, sloppy, and looked more like two five-year-olds fighting than two professional spies.
However, the greatest problem with this episode was the scenes in "Rio." Firstly, Lou Diamond Phillips's accent doesn't go anywhere near what a Brazilian accent sounds like. Secondly, the so-called party looked nothing at all like a party in Rio, and looked more like a "Brazilian Culture Appreciation Dance" than a legitimate Brazilian party. Even the background music was off: it sounded more like an American attempt at Spanish or Italian than Portuguese.
In spite of these flaws, I enjoyed this episode. I think Alex was brought in nicely and created a contrast with Carina's imposing, seductive personality. Morgan and Alex's relationship took a step forward (finally), while Chuck and Sarah resolved some of their issues. The "villain" of the episode was quite obvious, but it was entartaining to see Chuck guess which CAT was the bad one the first time, when he thought it was Amy because "no one's that perky." All in all, a good episode, but Chuck has seen better days.