If you’re looking for something other than a software unlock for your iPhone 4 baseband 2.10.04 / 3.10.01, Gevey SIM is the way to go. Now, as seen from the screenshots posted below which show an iPhone 4 on baseband 2.10.04 running on T-Mobile US network, Gevey SIM is also capable of unlocking iPhone4 baseband 2.10.04 / 3.10.1 in the US.
Gevey SIM unlock for iPhone 4 actually works by forcing baseband activation using the emergency dialer. Gevey SIM unlock for iPhone 4 is said to be vulnerable up to iOS 4.3 as well.
So if you can’t wait any more for the software based unlock for iPhone 4, you can use Gevey SIM to unlock your iPhone 4 on baseband 2.10.04 / 3.10.01 even on iOS 4.3. We at ChipHazard do not encourage you to use this method for unlocking your iPhone 4, due to its legal status. It is recommended that you wait for the 40 bit NCK for iPhone 4 from the iPhone Dev-Team to legally unlock your iPhone 4.