This is not live....they turned his mic louder from time to time (mainly at the ends of each song), and probably used a playback recording which was a little different to the one on the albums (they did the same on the history tour on some songs)...
Anyway, doesn't really matter, and to be honest, I even expected it to be playback, because that's what Michael was doing more and more starting with the dangerous tour. I always saw his concerts as an "entertainment show" with the focus on dancing and the choreography, so in my opinion miming is ok.
Regarding the actual video: What got me most was that he was sooo thin..his legs especially. And I am surprised that nobody here really mentioned that...I mean, everyone keeps saying "he looked awesome" etc., and that may very well be, if you are talking about his face and the emotions he showed. But I am completely honest with you: I couldn't imagine him doing it 50 times in a row, from a physical standpoint...
I liked his outfit VERRY much though. The jacket and the red shirt - looked amazing!