The iPhone Dev Team released version 0.9.11b1 of redsn0w last week that lets you restore IPSWs directly to your iPad 2, iPad 3 and iPhone 4S. This means recent iOS device owners can now downgrade their firmware using the jailbreak tool. This is good news for folks who updated to iOS 5.1.1 or iOS 5.1 and want to go back to iOS 5.0.1. You do need your SHSH blobs from the earlier firmware if you want to downgrade, but Cydia usually saves those files automatically for you. For detailed instructions, point your browser to the iPhone Dev Team’s blog.
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Redsn0w update lets iPad 2, new iPad, iPhone 4S downgrade to older firmware