The full changelog in Redsn0w 0.9.12b2:
“Update #1: Starting with version 0.9.12b2, redsn0w will now explicitly ask users with limera1n-able devices whether they want to inject rocky-racoon using the DFU ramdisk method, ro the backup/restore method (the ramdisk method is better for those with lots of media on their device that would create very large backups, and it’s required for those with unactivated iPhones). If you’ll always want to use limera1n, you can select that in the Preferences pane. It also fixes an iBooks issue an old-bootrom 3GS iPhones, and provides more useful error messages when things go wrong.â€
This version is only for those users who haven’t yet jailbroken their devices.. So if you have already jailbroken your Apple device with Redsn0w 0.9.12b1 I don’t see there is any point from re-jailbreaking your device with this new version.. If you haven’t yet jailbroken your iPhone. Here’s a quick guide showing you how to jailbreak your Apple device running on iOS 5.1.1 using Redsn0w.
Now I will give you the download links for this version of Redsn0w:
Download Redsn0w 0.9.12b2 [Mac users]
Download Redsn0w 0.9.12b2 [Windows users]