The PowerBook G4/1.25 15" (FW800) features a 1.25 GHz PowerPC 7447 (G4) processor with the AltiVec "Velocity Engine" vector processing unit and 512k on chip level 2 cache, 512 MB of PC2700 DDR SDRAM, an 80 GB Ultra ATA/100 hard drive (4200 RPM), a slot-loading 2X DVD-R/CD-RW "SuperDrive", a Firewire "400" and "800" port, built-in Bluetooth 1.1 and AirPort Extreme (802.11g), and ATI Mobility Radeon 9600 (4X AGP) graphics with 64 MB of DDR SDRAM in an attractive aluminum alloy case with a 15" widescreen TFT display (1280x854 native resolution). Custom configurations also were available.
The PowerBook G4 "Firewire 800" series adds AirPort Extreme (802.11g), Bluetooth 1.1, USB 2.0, and Firewire "800", as well as a faster logicboard and memory, to the 15" models.
Please note that unlike the otherwise similar PowerBook G4/1.0 15" (FW800), the PowerBook G4/1.25 15" (FW800) has the fiber optic based "ambient light sensor" that automatically "measures ambient light and works with integrated software to adjust keyboard illumination and screen brightness based on user preferences". The PowerBook G4/1.25 15" also has a faster processor, twice the default RAM, a larger hard drive, a more capable optical drive, and pre-installed AirPort Extreme (802.11g).
Also see: What are the differences between the 12-Inch, "Firewire 800" 15-Inch, and 17-Inch PowerBook G4 models introduced on September 16, 2003?