Just today I downloaded the 3.1 Beta version to my PC and sent it to the Kindle's root directory via USP. Once there, it installed itself automatically without prompting and rebooted the Kindle. That seemed a bit strange, as always before when I manually installed the bin file I had to cycle through the menus (Menu >Settings >Menu) and click on the "Update your Kindle" selection. But 3.1 is showing as the current version, and the "Update your Kindle" option is grayed-out.
Hmmm....