There's an app called SetiChatStatus. It's great! It fast and works in the background and it changes your status, at most, 5 seconds after the track changes in iTunes. It puts what you're listening to in iTunes as your status message. I'm using it right now. Check me out (AIM: marceline407@mac.com).
You can download it here:
http://www.versiontracker.com/moreinfo.fcgi?id=17192&db=mac
You can download it here:
http://www.versiontracker.com/moreinfo.fcgi?id=17192&db=mac