According to a USA Today article, Activision has turned to Jay-Z and Eminem to provide some added value to a special edition release of DJ Hero. In addition to the game, the bundle reportedly includes greatest-hits CDs from both rappers, possibly with new tracks; an "advanced version of the controller;" a DJ stand and a metal traveling case. The two musicians will serve as "consultants" to Activision, and will, of course, contribute tracks to the game.
Another collaborator, DJ Shadow, put four screenshots of DJ Hero up on his website that finally show some gameplay. It appears to be very similar to Guitar Hero, except sometimes the note line moves a bit, which we believe indicates switching tracks on the crossfader.