The iPhone 3G's Software Unlock is Updated
Right now this admittedly unscientific study shows only 35% of respondents have been successful using yellowsn0w. It's unclear why users would be surprised; this is an admittedly complex operation. Past successes by the iPhone Dev Team may have led people to be too optimistic.
Of course, as with many things of this nature (firmware upgrades, patches, and the like) it's not necessarily a good idea to be an early adopter.
- You need to install the latest 2.2 firmware (downloaded from here).
- Jailbreak your iPhone, using QuickPWN 2.2. Those using MacOS 10.5.6 need to re-enable DFU mode, which Apple disabled as a way to prevent Mac owners from jailbreaking their iPhones.
- You can install yellowsn0w 3G unlock by using either Cydia or Installer, add the yellowsn0w repository addresses posted on the iPhone Dev Team site to your installer application (iPhone Dev Team has requested no direct linking, possibly because they may change the location).
There's no PIN support yet. They are still working out the flow for SIMs with PINs enabled. You have to disable any PIN you may have on a SIM before trying yellowsn0w, for now.
And just a reminder from the iPhone Dev Team:
The iPhone 3G is used all over the world with all sorts of SIM cards, and we almost certainly will see untested and unexpected situations. If the soft unlock doesn’t work for you on day 1 (literally day 1, of 2009!) then please don’t panic or be impatient. This is new territory for everyone, so enjoy the ride as much as you can :)