As you know Apple scheduled iOS 6 public release on September 19th for iPhone 3GS, iPhone 4, iPhone 4S, iPod Touch 4G, iPad 2 and New iPad. If you are a developer or have the UDID of your device registered, then you can download the Golden Master release by Apple. This indicates that iOS 6 has already left its beta phase and, therefore, this build has many ballots to become the Apple publishes the 19th.
The iOS 6 Golden Master certainly has an added feature. iPhone 4S owners can now have a panoramic view of the new panorama mode in the Camera app. This new feature was presented during the keynote of Apple in the iPhone 5, but will also for iPhone 4S owners are available.
The Golden Master of iOS 6 carries the build number 10a403. Apple warns that after installing the Golden Master can not go back to earlier versions of iOS.