Amazon just announced a firmware update for the Kindle2. The K2 will finally get PDF support. This update will also include improved battery life. Amazon is claiming 85% longer run time with Whispernet on, but no improvement to the 2 week standby. It sound like they've added a standby mode to the software that manages the connection.
I went looking for the update and I found this page
. The update also adds to the K2 the ability to rotate the screen. Shiny.
US Kindle update
Int'l. Kindle update
Kindle DX update