That being said, bands who hire a sound-alike for the sake of one drive me nuts, I like it when a singer brings another dimension, like w/ AC/DC. I prefer Bon Scott, but Johnson definitely brings his own thing. I liked Tim "Ripper" Owens in Judas Priest
http://www.youtube.com/watch?v=6qd1iQscjFI
And sometimes when they bring in someone who sounds totally different, it's an epic fail, i.e Blaze Bailey w/ Iron Maiden, or John Corabi w/ Motley Crue.