The Rocky Racoon 5.1.1 Untether was just updated to version 1.0-2, and is now available for download in Cydia. This is the package that is installed on iOS devices that utilize the 5.1.1 untethered jailbreak, whether you obtained it via Absinthe, or via the Rocky Racoon installation on a 5.1.1 tethered jailbreak.

This update brings support to the iPhone 4 (GSM) 5.1.1/9B208 build that was recently released by Apple.

All that this means is that you can now gain untethered status using the latest version of Rocky Racoon. If your iPhone 4 is running this firmware build, and it is currently jailbroken using a tethered jailbreak, you can install Rocky Racoon to gain untethered status.

Special thanks to iH8sn0w for the clarification:

Even if you don’t fit the criteria to benefit from the update, it is still advisable that you update in order to be on the absolute latest build of Rocky Racoon. Have you updated yet?