The Dev-Team has added another update to their blog post about the ultrasn0w unlock for iOS 4.2.1. The update talks about an issue with retaining GPS when unlocking iPhones with 06.15.00 baseband. It seems that some people on 06.15.00 are losing their GPS functionality when they unlock their device. The Dev-Team does not currently have a fix for this problem and says that, even though the problem does not occur for everyone, you should just assume you will lose GPS capabilities when ulocking 06.15.00. However, they are working on a fix for the problem. Check out the full details below.
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).