1. There are profound issues with audio: it skips and stutters randomly. Apple has posted a Tech Note on the issue ("PowerBook G4 (Double-Layer SD) audio stutters or skips") but the solution doesn't work. Essentially, it implies that this machine is crippled. AppleCare either denies the existence of the problem or admits to it and offers no solution.
An Apple discussion forum article on the topic ("New Powerbook Audio Stutter / Looping / Echo problem") has over 387 replies (9,985 views) and it's just one of many posts. There are literally dozens of related mailing list, forum and blog postings on the matter. And while Jim Heid has posted a possible fix for the "Audio Echo" problem, but it doesn't work for everyone.
2. There are issues with the display: there is horizontal banding of every second or third pixel row over the entire screen. Each pixel row is darker or lighter than its neighboring pixel rows. This is a well documented seemingly ubiquitous issue over the entire line of new PowerBooks and again a problem that Apple does not acknowledge.
Some forum members have sent the computer in to AppleCare for repair for this issue and it was returned without any repair done the technicians claiming that the problem is "WITHIN SPEC" - meaning that the screen is within the model specifications and that it is not a problem. Some techs have even shipped a replacement display that exhibits the same problem.
Again, there are numerous posts about this issue.
3. There are issues with PowerBook (and Mac mini) SuperDrives being unable to burn DVDs at more than 2x regardless of the media used. What exactly Apple is going to do about these serious issues?
Many artists, audio and video producers that purchased top-of-the-line, professional quality notebooks for producing art, music and video aren't getting what they paid for.
More information can be found at http://powerbookdefect.info/