Apple today has released iOS 4.3.1 for iPhone 4, 3GS, iPad 2, iPad, and iPod touch 4G/3G. If you upgraded to iOS 4.3.1, and now you want to downgrade back to iOS 4.3, iOS 4.2.1 or 4.1, simply follow the instructions posted below to downgrade iOS 4.3.1 on iPhone 4, 3GS, iPod touch, iPad 2 and iPad 1 to iOS 4.3, iOS 4.2.1, 4.1, 4.0.x.