iliketheatre - Audra MacDonald was mic'd for her double bill at HGO. And that was with the orchestra placed behind her onstage at the smaller (1,000 seat) Wortham Theatre. She is apparently on the books to sing in the MET premiere of John Adams' "Doctor Atomic" in 2008-2009 and Chenoweth is still rumored to debut in 2009-2010 in "Ghosts of Versailles". So we will be able to judge for ourselves in a few years.
IssaMe - while Mr. Hadley has recorded "Candide" and "My Fair Lady", I believe he has yet to actually bow on the Great White Way... many opera singers have "crossed over" in this fashion (Doming, TeKanawa, Carreras, Ramey, Swenson, the list goes on and on)... but very few (Pinza, Tozzi, Stratas, Resnick come to mind) opera singers have actually performed on Broadway.
"When you're a gay man, you have to feel good about yourself when a urologist says, "Yeah. I pick you". - Happy Endings