From the technical download...
Found this in a download about the new powerbooks.
http://images.apple.com/powerbook/pdf/20051018_PowerBook_TO.pdf
Maximum battery life test. All PowerBook systems are capable of incredible battery life. Apple tested the PowerBook G4 in several usage scenarios, using energy-saving features built into Mac OS X, to gauge what users can expect in terms of maximum battery life.
Wireless productivity test. All PowerBook G4 computers have built-in AirPort Extreme wireless networking to make staying connected as easy as possible.4 Apple tested wireless battery life by alternately loading web pages over an AirPort network and editing a text document, never letting the system go to sleep during the test. This is a typical scenario of computer use on the go, resulting in a battery performance number that is very relevant to mobile users.
DVD playback performance test. Every PowerBook comes standard with a DVD player for DVD movie playback. Viewing a DVD movie usually takes two hours and is an experience that shouldnt be interrupted by the need to recharge or swap the battery. PowerBook battery life for this system-intensive activity was tested by playing a complete DVD movie in full-screen mode at full screen brightness.
Battery life performance results
17-inch PowerBook G4 (1.67GHz)
Maximum Up to 5 hours, 30 minutes
Wireless productivity Up to 4 hours, 15 minutes
DVD playback Up to 2 hours, 30 minutes
15-inch PowerBook G4 (1.67GHz)
Maximum Up to 5 hours, 30 minutes
Wireless productivity Up to 3 hours, 45 minutes
DVD playback Up to 2 hours, 15 minutes
12-inch PowerBook G4 (1.5GHz)
Maximum Up to 5 hours
Wireless productivity Up to 3 hours, 45 minutes
DVD playback Up to 2 hours, 45 minutes
Testing conducted by Apple in September 2005
using preproduction PowerBook G4 units. Battery
life depends on configuration and use.
3 hours 45 min productvity sounds good. Taken with or without grains of salt?