As expected, Apple has just released iOS 4.3.1 for iPhone 4/3GS, iPod Touch 4G/3G, iPad 2/1. Along with some minor bug fixes, iOS 4.3.1 also comes with a fix for graphic glitches issue experienced by iPod Touch 4G users, resolves authenticating issues with enterprise services and fixes various bugs when activating and connecting to cellular data networks. iOS 4.3.1 also bring some improvement in battery life for all supported iDevices.
If you rely on a jailbroken or unlocked iPhone, STAY AWAY form iOS 4.3.1 until proper jailbreak and unlock tool is released by iPhone Dev-Team. Chronic-Dev Team is already working on GreenPois0n tool for iOS 4.3.1/4.3 jailbreak. It is still not know whether Apple patched the userland vulnerability used by Comex to jailbreak his iPad 2 on iOS 4.3.
You can update to iOS 4.3.1 directly using iTunes. Just connect your iDevice to your PC or Mac via USB cable and hit the Update button.
Alternatively you can use the links below to download stock iOS 4.3.1 IPSW for your iDevice and restore it manually through iTunes:
iPhone 4 (GSM) » iPhone3,1_4.3.1_8G4_Restore.ipsw
iPod touch 4G » iPod4,1_4.3.1_8G4_Restore.ipsw
iPod touch 3G » iPod3,1_4.3.1_8G4_Restore.ipsw
iPhone 3GS » iPhone2,1_4.3.1_8G4_Restore.ipsw
iPad (1st-Gen) » iPad1,1_4.3.1_8G4_Restore.ipsw
iPad 2 (WiFi) » iPad2,1_4.3.1_8G4_Restore.ipsw
iPad 2 (GSM) » iPad2,2_4.3.1_8G4_Restore.ipsw
iPad 2 (CDMA) » iPad2,3_4.3.1_8G4_Restore.ipsw
Update 1: Downgrade iOS 4.3.1 to iOS 4.3/4.2.1/4.1/4.0 or iPhone OS 3.1.3/3.1.2
Update 2: Jailbreak iOS 4.3.1 on Mac OS X Using PwnageTool 4.3 [Untethered]
Update 3: Jailbreak iOS 4.3.1 with Redsn0w 0.9.6RC9 on Windows & Mac [Untethered]
Update 4: Jailbreak iOS 4.3.1 on Windows Using Sn0wbreeze 2.5 [Untethered]