in the thread below, i posted results of my tests with my sony dru500ax and dvd-r 4x media. i tried both video and data and my results were a little disappointing as most burns were at 2x.
http://www.cdrlabs.com/phpBB/viewtopic.php?t=12152
after doing some research, it seems others have had problems getting consistant 4x burns with this drive. have you had good luck with 4x burns and what media are you using?