Castle gets a lot of things wrong. It wildly misrepresents--or, at best, cherry-picks--the experience of being a bestselling novelist or a New York City detective. But damn that smarmy motherfucker Nathan Fillion. He's just so entertaining to watch.
Also, as Leverage showrunner John Rogers notes, the techie clues have been real smart so far. I still don't buy Stana Katic as murder police, but I'm giving her Kate Beckett character the benefit of the doubt for now. Maybe the writers will come up with an interesting and plausible backstory for her.
The fourth episode was the one that really sold me. Lots of nice little moments, including the uniform searching the dumpster, Castle and his daughter cutting onions, and the closing scene in the bookstore. You can get the full show from iTunes. Here's the Lame TV PreviewTM:
Episode three wasn't bad, either. Like everyone else, I really enjoy the father-daughter scenes with Nathan and Molly. And I'm thinking about making my own "You Should Be Writing" screensaver.