I get 4 hours compared to 5 under OS 9, and the list goes something like this.
- Display brightness
- Audio (mute audio will cut power to audio hardware)
- Hard disk sleep (OS 9 had option to sleep manually, hence slightly better)
- RAM disk in OS 9 helped reduce access to hard disk and could let you push out batt life to 6 hours plus.
- Peripherals (such as mice, USB powered devices)
- Processor speed under OS 9 could be reduced when on battery power.
and lastly
- OS 9 had a consumption meter, so you could tell how changes were affecting your battery usage.
I hope OS X catches up soon.