(Tim) Updated to the latest version of iTunes, when I started the application just now, I got a message window announcing iTunes DJ. They tell me "iTunes DJ automatically picks songs to make a continuous mix of your music." And if I'm the host of a party, it will "allow guests to request songs using the Remote application for iPhone and iPod Touch."
I clicked the window closed and was presented with this first iTunes DJ selected playlist. Thought you'd all get a kick out of it.

