According to the change log:

Version 3.0.2 (11/05/2004)
What’s New in this Version
The DVD Studio Pro 3.0.2 update is strongly recommended for all users of DVD Studio Pro 3. In addition to improving general stability and compatibility for double-layer media on supported systems
Be warned that this update screws up a lot. Many users are reporting upside down menus and other crazy quirks.

If your 3.0 is working fine, don't mess with the "suggested" update.

You've been warned.