From my searching around differeent forums I have found that the new 2.1 upgrade for the 2G iPhones baseband remains the same ( 04.05.04_G ).
And there iPhone remained UNLOCKED.
The 3G iPhone upgraded to 2.1 via iTunes has a baseband of ( 02.11.07_G ).
Different phone = Different software than the G2 iPhone.
So I'm assuming that upgrading your G2 iPhone via iTunes would keep the unlock?
Can we have some confirmation on this.... PLEASE
Also do you have to use iTunes8 or iTunes 7.7? Or does it matter..