Earlier this week Dev Team releases Ultrasn0w 1.2 Unlock for iOS 4.2.1 and we posted guides to Upgrade iPhone 3G, 3GS Baseband 06.15.00 with PwnageTool Unlock Edition. Some random iPhone unlockers noticed that by unlocking the baseband with Pwnage Tool unlock edition or Redsn0w beta 5 achieved a significant loss of GPS signal, in fact, the Dev Team has just formalized it through an update included in the official blog.
Update # 5: Unlockers have been reporting mixed results about GPS functionality at 06.15.00.
Until we can track down what differentiates those who retain GPS vs. those who lose it, be conservative and assume you’ll lose GPS at 06.15.00.
As we work on finding the cause (and possibly a fix), please report your personal findings in our comments section.
(Update: early indications are that while 06.15.00 is capable of GPS, it will require some further hacks. But please still be conservative and assume you will lose GPS at 06.15, in case the hacks don’t work).