A fun toy, maybe, maybe not. I though Craigs singing of the national anthem sounded pretty professional. I have heard so called PRO singers that sounded terrible compared to his performance. Many times. And they got paid a lot of $$.

Would I use it on stage (If I performed on stage)? Maybe. depends on the venue I think, IMHO. Think about it...I recently stopped over to hear a friend play at a nursing home...he played well, and sang only so/so...if he used this, and sounded super....do you think the audience would care? Maybe, maybe not. I think most would love to hear the great vocals, and these venues typically just mean playing the song straight away.
In a club ect...probably not.