Apple has a new tech note out, "PowerBook G4: Faint White Spots in Display", the crux of which is that if your PowerBook's serial number falls within a certain range, it qualifies for a free LCD replacement. This is of course, assuming that your PowerBook is exhibiting the "faint white spots" phenomenon. So, I called AppleCare this morning, and the gentleman on the other end of the phone told me that my PowerBook did fall in the affected serial number range, and that my options were to send it to Apple, and they would repair it if they felt that the display was defective, or I could take it to an Apple authorized repair center, which could presumably make the judgment about the display and go from there.
Reading more about this issue on the web, I don't think that my display suffers from the "white spots" problem. I think that the lower-right quadrant of the display is a little dim, but that is all. Basically, I don't think that I'm getting uniform brightness from my display, which sounds like a different (and probably not covered) issue from the white spots. Of course, it could all be in my head....
-Andy.