I downloaded it and i'v egot it up and running. The only nussence is having to open the itunes growl program everytime i turn the computer on. Unless I have it configured wrong, it's a seperate app from growl, so it's a set of headphones next to the claw on the top of my screen (where the clock, bluetooth, airport, etc are)
Just add GrowlTunes into your Login Items tab of your System Preferences>Accounts and it will load on login.