I have taken the bus quite a few times in and out of NYC, and I agree that checking out the line about an hour ahead is very important. Although they will likely put more buses on the route if there are too many people, sometimes this takes HOURS!
Good Luck!
Shows seen in 2011: Rock of Ages (WE, Shaftesbury Theatre - 7 Oct), Jersey Boys (WE, Prince Edward Theatre - 1 Sep), Cirque du Soleil: Zarkana (Broadway, Radio City Music Hall - 26 Aug), RENT (Broadway, New World Stages - 25 Aug), Hair (Broadway, St. James Theatre - 24 Aug), The Book of Mormon (Broadway *WON LOTTO*, Eugene O'Neill Theatre - 24 Aug), Dress Circle Benefit Gala (WE, Her Majesty's Theatre - 7 Aug), Derren Brown: Svengali (WE, Shaftesbury Theatre - 6 July), Lend me a Tenor the Musical (WE, Gielgud Theatre - 3 June), Lord of the Flies (WE, Open Air Theatre in Regent's Park - 2 June), In a Forest Dark and Deep (WE, Vaudeville Theatre - 31 May), Jersey Boys (WE, Prince Edward Theatre - 28 May), The Umbrellas of Cherbourg (WE, Gielgud Theatre - 2 May), Priscilla Queen of the Desert (WE, Palace Theatre - 29 Apr), Les Miserables (WE, Queens Theatre - 20 Apr), Thrill me (WE, Tristan Bates Theatre - 14 Apr), Ghost the Musical (Manchester, Opera House - 13 Apr), Million Dollar Quartere (WE, Noel Coward Theatre - 5 Apr), The Lion King (WE, Lyceum Theatre - 16 Mar), The Exonerated (WE, Charing Cross Theatre - 15 Mar), The Children's Hour (WE, Comedy Theatre - 14 Mar), Clybourne Park (WE, Wyndhams Theatre - 12 Mar), Company (WE, Southwark Playhouse - 12 Mar), The 25th annual putnam county spelling bee (WE, Donmar - 2 March), Jersey Boys (WE, Prince Edward Theatre - 11 Feb), Million Dollar Quartet (WE, Noel Coward - 9 Feb), Love Story (WE, Duchess Theatre - 7 Feb), Lance Horne:First things last (WE, Garrick Theatre - 30 Jan), La Boheme (WE, Soho Theatre - 29 Jan), Legally Blonde (WE, Savoy Theatre - 10.Jan)