John Mayer is hands down one of the best live shows anyone could possibly see. I've been to 4 myself... have recordings of 40+, and they're unbelievable.
I think people should drop their opinions based on Your Body is a Wonderland and Daughters and actually listen to "Continuum" or "Try" or any of his stuff with Buddy Guy, Sly and the Family Stone, John Scofield and form your own opinion.