One thing I love about Sondheim is that he isn't afraid of nastiness; he does not need to make his characters meek and charming. Mary, in "Merrily We Roll Along," is like a new version of Sally, from "Follies." We may feel for Sally, but she isn't a little lamb. She would gladly toss her husband under a bus--if this means a shot at the guy she is really pining for. On her wedding night, she makes a shocking observation, in the company of her spouse: "Love will see us through till something better comes along...." Mary has Sally-esque qualities. Trapped in her unrequited love for a worthless man, she makes bitter jokes about the people who actually do clear their schedules for her. ("I lost 180 pounds....but he still calls....") Mary's ugliness is especially flagrant at a party, where a friendly stranger compliments her book: "I've read it and re-read it." Instead of accepting the compliment, Mary offers this gratuitous...