Fun news: Downgrading from iPhone 1.1.3 bricks your phone (restrictions apply)
December 30th, 2007
If your iPhone has never been unlocked, downgrading from 1.1.3 will leave you bricked until you upgrade back to 1.1.3, as far as I can tell. The phone (even with an authentic AT&T SIM) reports an Incorrect SIM while iTunes says there's no SIM at all, when you've downgraded back to 1.1.1 or 1.1.2 (1.0.x untested). If your phone was unlocked, the baseband upgrade fails on 1.1.3, so you will not have this problem but will not get 1.1.3 to work.
Obviously this may change once Apple releases the firmware officially but I do not count that as likely.
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