I'm with Jinx. I love the show, but I really almost hated the S4 premier. Did they change writers or something? I've come to expect intelligent plots, but this episode was cliché, predictable, and everything was resolved way too handily. The whole formula for the show seems to have altered. One of the things I liked most about the show was that the characters were so supportive of each other. Now things have turned Grimdark™. There's some scary-evil conspiracy monster overshadowing the whole vibe, the new Captain is a stereotypical bitchy-female-in-charge type, Beckett has serious mental issues, and Castle's daughter has a whole new bitchy-disrespectful-teenager personality! Plus, Beckett's new hair/makeup makes her look like a hooker.
On the other hand, Castle's admission that he loved Kate painted the writers into an impossible corner. Shows tend to self-destruct when the main characters finally actually get together. So maybe they did the best they could to extract themselves from that situation, and things will pick up again from here on out. Keeping my fingers crossed.