Apple have just rolled out iOS 4.1 update for iPhone and iPod Touch. Official release notes highlighting core iOS 4.1 features are as under:

This update contains improvements, including the following:

• Game Center
  – Send and receive friend requests
  – Invite friends to multi-player games over the Internet
  – Play multi-player games by auto-matching with other
     players
  – View Leaderboards and Achievements
  – Discover new games from friends
• High dynamic range (HDR) photos on iPhone 4
• Support for TV show rentals on iTunes
• Ability to upload HD videos to YouTube and MobileMe
   over Wi-Fi on iPhone 4
• Additional support for AVRCP-supported accessories,
   including next & previous track control
• FaceTime calling directly from Favorites
• Bug fixes, including:
  – iPhone 4 proximity sensor performance
  – iPhone 3G performance
  – Nike+iPod fixes
  – Bluetooth improvements

Products compatible with this software update:
• iPhone 4
• iPhone 3GS
• iPhone 3G
• iPod touch 2nd generation, or later

Game Center requires iPhone 4, iPhone 3GS, iPod touch 2nd generation or later.