Apple has released a new update for users of iPhone 4 GSM, released as iOS 5.1.1 (9B208) and is meant to address few stability issues with the device. As of now, there is no change-log of the released update from Apple, and the released note states that it is strictly meant for GSM iPhone 4 users only.
For the users who have a jailbroken device, we would request you to say away from updating your iPhone 4 GSM to iOS 5.1.1 as we don’t have a confirmed working jailbreak for the release. However, few users are reporting the success in jailbreak. Below is the direct download link of iOS 5.1.1 (9B208) for GSM iPhone 4.
Download iOS 5.1.1 (9B208) for GSM iPhone 4 [Direct link]