Florence gave an excellent performance @Bonnaroo. Live performances are always subject to environmental conditions of one kind or another. There isn't the technical control you'd get in a recording studio or in front of a studio camera. Sometimes the show must go on regardless of how the performer may feel.
I love Florence + The Machine. She's one of my 2 favorite artists in the world. But this wasn't her best live performance. I know an artist sweats on stage, but she looked sick. And I missed the choir. :(