If I remmeber correctly I've seen them as an opener, and they were horrible. I might be wrong though.
Btw, Dragonforce doesn't even play all of the song, they have a soundtrack playing in the backround for guitars.
But I have Nine Inch Nails on November 9th (should have been last friday). I'd really like to see AC/DC when they come around. Also if Queens of the Stone Age ever had another concert I'm definetly going to that, that was the best one I've been to.