iPhone OS 3.1 software update has been released and available for download through your iTunes or you can download manually here. While you’re downloading the update, you might want to read iPhone 3.1 software walkthrough posted by The iPhone Blog. If you insist to update your iPhone after reading the walkthrough, make sure you’ve also read Rock Out without Lockout from iPhone Dev Team, which is trying to warn the iPhone 3G/3GS owner that is updating to firmware 3.1 as you’ll lose the ultrasn0w unlock.
Click here to check wether your iPhone is locked to any network carrier according to your country. If you found that your iPhone is locked, you can update your iPhone with Pwnagetool that won’t update its baseband version. There are iPhone in certain countries are unlocked sets, including Hong Kong, Malaysia, New Zealand, Italy and more. And if you’ve noticed that iPhone in Singapore is also an unlocked set, I can restore or update my iPhone to firmware 3.1 without caring too much about the ulrasn0w unlock.
Are you going to press the update button on your iTunes?
P/S: You can Jailbreak your iPhone 3.1 with Pwnagetool 3.1.