iPhone update 3.1.2 (241.7MB) is out today with the following fixes:
• Resolves sporadic issue that may cause iPhone to not wake from sleep
• Resolves intermittent issue that may interrupt cellular network services until restart
• Fixes bug that could cause occasional crash during video streaming
You’ll get a carrier file update after the initial installation. Also, if you are AT&T tethering or Jailbroken, you might want to hold off. The update is also available for the iPod Touch.