Stephen Sondheim, the patriarch of American musical theater, weighs in on the “heavily revamped version” of The Gershwins’ “Porgy and Bess,” a current hit on Broadway, in an interview with The New York Times’ Anthony Tommasini:
http://www.nytimes.com/2012/03/11/arts/music/some-ground-rules-for-revising-operas-and-musicals.html