I take the Amtrak in the East quite regularly, and have been most pleased. I suppose it is alot like flying. If you do it enough, you learn the tricks, which trains to book, and so forth.
My experiences have been in the Newport News / Richmond, Va to Washington, DC to Philadelphia to New York corridor.
1st rule: Metroliners are preferred. Coach seating is one step up, and the train is express.
2nd rule: Club Service is great. For roughly 2x the fare of a coach ticket, you get REAL first class service. Good food, extra room, eating at your seat, curtains, etc.
3rd rule: If you can't get Club, get Custom Class. A bit more room, and very few crying babies.
John