Thanks again to the iPhone dev team there is already a solution for this, once you have jailbreaked your iPhone:
- make sure your iPhone indeed runs iPhone OS 3.0 and Cydia is already installed and working!
- open Cydia, the first time you open Cydia it does some cleaning and reorganisation, so if it closes after you opened it, just try again.
- add the repo repo666.ultrasn0w.com to Cydia. That last “o” is actually the number zero “0”!
- search for ultrasn0w and install it
- reboot your iPhone
- T-Mobile USA users should disable 3G before using ultrasn0w
Remember: jailbreaking / unlocking your device might void your warranty! You do that on your own risk, if your iPhone breaks, we are not resposible for that!