I can agree with you there. Ozzy definitely sounds better in 2013 than he has since at least 2005, perhaps even earlier.
I just wouldn't say he sounds "great", not even for his age.
I thought the reunion show sounded good... even listening to the audience recording before the official version was released. Yes, Robert Plant has lost some of his vocal range, so couldn't sing the songs exactly as they were written. But that's not the same as having your voice crack and singing off-key.