The one of reasons is that AppleGraphicsPowerManagement is not working normally.
Need some testing here in this thread with and without this kext (it was changed by me, so, just put it to extensions, check out graphic card ID and your macbook model).
Please write results here with and without this kext.
I strongly recommend to all to use this patch. I have finally done testing, it's working. You only need to open info.plist in it and change your Mac model, probably we have different.
The result of this patch is that battery will work double time, little less than in windows, but very good.
I have 7800mha battery here (the biggest one), it works in mac os x now 4hours 30 minutes in surfing internet mode.
Before it worked around 2 hours 10 minutes.
All tests were done in CLEAN system. Tested in 10.6.3, 10.6.7 and 10.7.2 11C35.