It might be overstated to say it all goes back to Jon's voice, but that is undoubtedly a big part of it. I can remember his vocals sounded noticeably better in the summer shows last year (especially Live Earth). And even on this tour prior to the nefarious 'Japan' incident, Jon sounded pretty good and the band was performing fairly well, they just were putting out pretty shitty sets. I think he's started giving a shit about his performance again outside of the ass bullshit, and the effort he's put into it the past year or so is showing, especially in the past few months.