The first half of My Worst Nightmare contains some of the best comedy and the biggest laughs of the season, and the second half … eh. So there we are: half of a terrific comedy, followed by half of an improbable and only mildly interesting romance. That’s an even proposition, and when it comes to movies, an even proposition isn’t good enough for most people, but here’s a case where it might be. — Mick LaSalle