i can now report that this basically worked. i say "basically" because it wasn't really "for free." i got a 32 GB iphone 5 for $299 and sold my unlocked 32 GB iphone 4 for $230. still, a $69 new 32 GB iphone 5 was a really good deal.
the only real snag was successfully unlocking my old iphone 4 work. the directions that AT&T emailed me when it authorized the unlock left out a critical step (remove the SIM card after backing up and wiping the phone, but before restoring from backup). so i wasted a bunch of hours repeatedly wiping my phone and then restoring it from backup before i found the missing step mentioned on an apple support page.
the only real snag was successfully unlocking my old iphone 4 work. the directions that AT&T emailed me when it authorized the unlock left out a critical step (remove the SIM card after backing up and wiping the phone, but before restoring from backup). so i wasted a bunch of hours repeatedly wiping my phone and then restoring it from backup before i found the missing step mentioned on an apple support page.
