Around 2.5 hours on CPU 'automatic performance' setting...
About 4.2 hours on 'low'.....
And....(I love this one) 40 minutes on 'maximum setting'.
Also, the battery is loose and it wobbles (very annoying). Not to mention the keyboard adhesive problems.....*sigh*. If you haven't heard, the keyboard is held onto the computer with tape. It's very cheap tape. And, if you're lucky (like me), your keyboard keys (mostly K, L, Arrows, Right Shift) have a weird sort of 'sticky' feeling to them. That's the key tapping against the top of the computer case, thanks to faulty tape.
Probably the most depressing discoveries after spending $2,524...I hope I don't run into any more. If I do, I may be forced to get a PC notebook next time...
I must admit, my old 12" felt a lot more 'solid'. If it weren't for those two flaws, I would be 100% satisfied with the computer.
But to answer your question...I don't mind the battery life. For browsing / chatting / simple things...dim the screen to '1' brightness, set the CPU to 'low' in the energy saver and you're looking at around 4.2 (or more) hours of usage. Sadly, battery life for gaming / dvd viewing / burning or ripping dvds / video editing / music production / anything else a powerbook is purchased for instead of an iBook is pretty....what's the word? Oh yeah, 'lackluster'...