With the release of Mountain Lion, users were upset to find that battery life had been reduced by over 30%. OS X 10.8.1 improved things somewhat but not to pre-Mountain Lion levels. Now tests completed by The Mac Observer show battery life returning to approximately 380 minutes with a 2011 MacBook Pro.
The big change came with 10.8.2, which is still undergoing developer testing. Using the latest build, 12C35, we saw a tremendous increase in battery life, to the point where running time was a few minutes longer than even that of 10.6.8.
We must reiterate that 10.8.2 is still a work-in-progress and is subject to change before it is released to the public. We do not know what changes Apple has made to Mountain Lion's code to account for the battery life increase, or if those changes must necessarily be reversed before release, but we hope that Apple will find a way to preserve the battery life improvements in future Mountain Lion updates.
Read More [via Adam]