I liked Castle, personally. You have to watch the whole episode - I think it gets better. Also, for the sake of all new series, if the first episode is mediocre or better, I'll give the series 4-6 episodes to see if it improves; if not, no big loss. If the first episode is godawful, I may or may not (depending on the cast) give it a second episode just in case the first was a fluke. Sometimes the writers change enough to make a second episode watchable.

I adore Nathan Fillion enough (and liked the first episode enough) that I'm willing to see this series through at least a few more episodes (and hopefully Nathan will get a good run out of this series)!