A user named Cynikal has created a firmware hack that enables the PowerBook SuperDrives to burn at their full capability - that is, burn DVD-Rs at 2x, burn and erase previously unusable DVD-RWs, and burn CDs at 16x. This hack is possible because the drives included in PowerBooks can, unmodified, burn the above formats, but have been disabled from doing so. Visit the above link for more information; an upgrade and downgrade are provided, and have worked as advertised for me.
[robg adds: As with anything that modifies your firmware, exercise caution to insure that the process is not interrupted!]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030818164328868