If you're an iPhone 3GS or iPhone 4 ultrasn0w user who held off on updating to iOS 5 in order to maintain your SIM unlock, the moment you've been waiting for is here. The iPhone Dev Team has released an update for the software and as usual, the process isn't for the faint of heart. First, you'll have to compile a custom IPSW iOS 5 file to preserve your modem firmware, and then use redsn0w to jailbreak before you can finally unlock your iPhone using ultrasn0w. Keep in mind that the jailbreak's tethered, so you'll lose it if the phone reboots or powers off, but you can re-jailbreak by running redsn0w again. In addition, only the 01.59.00 modem firmware for the GSM iPhone 4 and a few others for the 3GS support this unlocking method. That said, it's one of the few options if you want a SIM unlocked iPhone — not everyone can afford an unlocked iPhone 4.