Apple has recently made available the latest iOS 5 GM (Golden Master) version to Apple developers. This is the last beta of iOS 5 from Apple. This is only available to developers yet.
The full and final version of the iOS will be available on 12th October 2011 to everyone.
IPhone Dev Team & iH8Sn0w also updated their jailbreak tools to provide tethered jailbreak for iOS 5 GM. redsn0w 9.9b3 and sn0wbreeze 2.8b8 are available for download now.
Sn0wbreeze lets you update to a different iOS version while preserving the baseband. Baseband preservation is needed for  Rebel Micro Simcards to use the iOS 5.0 GM.
Good news is that Rebel Micro Sim works on iOS 5 GM while preserving older baseband (04.10.01 & below). So now you can unlock iPhone 4 on iOS 5 GM using Rebel Micro Simcard.
Here are the screenshot:

Unlock iPhone4 iOS 5 GM Rebel Micro Simcard













What does GM (Gold Master) mean ?

The final beta version of a program that is ready to be released to the public. The entire goal of the beta process is to arrive at the gold master candidate. Once it is tested successfully, it becomes the gold master and is shipped out to be duplicated (if it’s a CD or floppy) and/or uploaded to the Web. The process of creating the gold master is often referred to as “going gold,” or you could say that certain software “went gold” when the golden master was released.

Here’s the history of the released bits of iOS 5:

Apple has released 7 beta versions of iOS 5 that unveiled most of the new features of the revolutionary iOS 5 firmware.
iOS 5.0 beta 1 on June 6th.
iOS 5.0 beta 2 on June 24th –
iOS 5.0 beta 3 on July 11th –
iOS 5.0 beta 4 on July 22th –
iOS 5.0 beta 5 on August 6th –
iOS 5.0 beta 6 on August 19th –
iOS 5.0 beta 7 on August 51st –

Download iOS 5 GM ipsw firmware
Download iOS 5 GM for iPhone 4 (GSM)
Download iOS 5 GM for iPhone 4 (CDMA)
Download iOS 5 GM for iPhone 3GS
Download iOS 5 GM for iPad 2 (Wi-Fi)