I know I'm a tad bit late, but here is the list of things that apple has updated in 3.1
iPhone OS 3.1 includes these features and updates:
- Improved syncing for music, movies, TV shows, podcasts, and photos1
- 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 a 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
