Just a couple of days ago Apple had released the iOS4 for its iTouch line-up. Yesterday, the folks behind redsn0w released an update of their application which allowed users to hacktivate iOS4 on their iPhone 3G, and jailbreak iPhone 3G/iPod Touch 2G. Now the folks behind PwnageTool have released an updated version of their application.
The PwnageTool works only on previously jailbroken iPhone 3GS having an old bootrom. The application does not support the latest bootrom. Therefore, users who are still stuck on jailbroken iPhone OS 3.1.2 can now upgrade to iOS4 via PwnageTool 4.0. They will retain their jailbreak after the update. iPhone 3G owners can update to iOS4 by restoring an ipsw created from PwnageTool 4.0 via recovery mode or DFU mode.
Sadly, the Pwnage Tool 4.0 does not support the iPhone 2G, the original iPod Touch, and the iPod Touch 3G. Here is the link to the post with detailed instructions for different iTouch devices from Apple.