Personally, I'm not a big fan of pitch correction when you can't monitor the original without the audience hearing it.

In most cases, the singer hears their own voice, and the audience hears the pitch corrected version. If you can't hear your OWN voice, it's hard to tell how far off you are, when your head voice is drowned out by the processed one. In the studio, the artist NEVER hears the pitch correction until afterwards.