Remember msft.guy? who fixed the blacksn0w unlock for iPhone 3.1.3 05.11.07 baseband? and who recently released binary which enabled blacksn0w unlock port for iPhone 3GS, on iOS 4 Beta 4 (formerly iPhone OS 4).
Well the guy is back now! He has posted PwnageTool bundles for iPhone 3GS, iOS 4 GM release which you can use to jailbreak your iPhone 3GS, while preserving your baseband so that you can unlock using ultrasn0w or blacksn0w.
The description of the bundle, as posted by msft.guy is as follows:
3GS GM bundle.. Don’t forget to update Cydia or add OpenSSH and OpenSSL
Since I haven’t tried this bundle yet, I cant really comment on how well it works. So I will recommend you to stay away unless you are a very advanced user and know your iPhone inside out.
And since the iPhone Dev Team has already promised to release full jailbreak and unlock for iOS 4 sometime this month, I will highly recommend you all to wait for the official PwnageTool 4.0 release before messing around with your phone. Stay tuned for more updated on this space!