Success: 2.2.1 to 3.0 locked to 2.0.2 unlocked to 3.0 UNLOCKED!
I was very anxious to use 3.0 (don't ask why ;)).
I had my unlocked-jailbreaked iPhone 2G with 2.2.1, and i restored by mistake to 3.0 GM.
So i ended up with a beautiful locked iPhone, even if the carrier Claro is an authorized carrier in Argentina.
So, after reading, this is what i did.
NOTE: i had installed iTunes 8.2.
1) Sync your iPhone
2) Go into DFU mode
3) iTunes would open, and you should shift+RESTORE to 2.0.2 FW.
4) Jailbreak 2.0.2 with Quickpwn RC3 (DO NOT INSTALL CYDIA, JUST UNLOCK).
5) Go offline (iTunes should NOT be able to reach internet)
6) Start iTunes and shift-UPDATE to 3.0 (do not use "Restore")
7) Sync your iPhone again.
Now i have 3.0 working fine.