I made an observation when upgrading to 3.1.3 that I do NOT remember noticing before, and I thought I'd share since it could certainly affect me in the future, and possibly others. When upgrading one device to 3.1.3, it now dumps the previous .ipsw files for ALL devices into the trash - not just the one you're upgrading/replacing. If you want to keep them, make sure you move them out of the trash. This is particularly important to note for someone like me, who has a jailbroken device that I don't intend to upgrade AND a newer iPhone that I AM updating. I saved my 3.1.2 .ipsw files from the trash and have put them elsewhere incase I need to restore my jailbroken device before 3.1.3 is cracked. Just FYI. I apologize if this has been noticed & pointed out before.