[Updated] Let’s clear the basics out of the way first. U2 were really good and at times thrilling at the Mercedes-Benz Superdome Thursday night. Musically, they’re a machine that at times sounds like one instrument behind Bono, which means they always seem in step with each other. And Bono is a genuine rock star. When he stood alone on the stage located about 20 feet into the audience, he seemed most at home. The space and an audience close enough to touch clearly energized him.