Apple has just made available through iTunes iPhone OS firmware version 3.1.1 (or just 3.1 as many are calling it). Its a major update covering a number of new fixes and support for the new iTunes 9 (full details of the software update after the break) However, if you’re an iPhone 3G / 3GS user, and you have unlocked your iPhone using the iPhone Dev Team’s ultrasn0w unlocking tool / software / application, you are advised to hold back just for a few days.

Here are the highlights of what’s new to the new iPhone / iPod Touch OS 3.1.1…

• Improved syncing for music, movies, TV shows, podcasts, and photos
• iTunes U content organization
• Redeem iTunes Gift Cards, codes, and certificates in the App Store
• Display available iTunes account credits in the App Store and iTunes Store
• Save video from Mail and MMS into Camera Roll
• Option to Save as new clip when trimming a video on iPhone 3GS
• Better iPhone 3G Wi-Fi performance when Bluetooth is turned on
• Remotely lock iPhone with passcode via MobileMe
• Use Voice COntrol on iPhone 3GS with Bluetooth headsets
• Paste phone numbers into the keypad
• Option to use Home button to turn on accessibility features on iPhone 3GS
• Warn when visiting fraudulent websites in Safari (anti-phishing)
• Improved Exchange calendar syncing and invitation handling
• Fixes issue that cause some app icons to display incorrectly

If you’ve already got an unlocked iPhone 3G / 3GS, it is suggested that you wait a few days (to a week or so) so that the iPhone Dev Team will have the time to update their tools.

If you update to Apple’s new software using the normal iTunes process, you will lose your ultrasn0w unlock. In fact you may lose it permanently, because for most people the baseband firmware cannot be reverted to a previous version (unlike the main application CPU firmware).

[via iPhone Dev]

We’ll update everyone, once a new Pwnage Tool is available, this will likely help bypass any permanent update to your iPhone 3G / 3GS’s baseband, etc when you undergo the upgrade process.