Kindle Battery Update.. Not For Most People
It has been widely reported that the recent Kindle firmware update improved battery life up to 85%. Unfortunately, this is not true for almost all Kindle owners. The battery life improvement only applies to the recent Kindle 2 (Global Wireless) version that was introduced October 7, 2009. The original Kindle and Kindle 2 (U.S. Wireless) version see no such benefit. Amazon points this out in a roundabout way on their site.
The Kindle 2 (U.S. Wireless) version does get the other benefits like built-in PDF reader and manual screen rotation.