Yesterday Apple released the Golden Master ("GM") version of iOS 6 to its registered developers so that they can test it for any last minute show stopper bugs before it gets publicly released on September 19. The GM build is 10A403 while the last developer build (beta 4) released on August 6 was build 10A5376e.
Unlike the four beta builds that preceeded it the GM isn't available as an Over The Air (OTA) download. It's only available as a binary download from Apple's developer portal and is quite large in size. The iPhone 4S package weighs in at 957MB while the iPad 3 bits are 1.15GB.
As per usual, Apple reserved a few new features for the GM that weren't in the previous developer builds (Tweeting and Facebook posts from Notification Center come to mind). It also includes a number of refinements and enhancements as expected.
Apple made some significant changes to the new Maps app in the GM, adding new flyovers for New York City and Rome and changed the flyover icon from the rather pedestrian looking "3D" characters to three shaded buildings (pictured).
AppleInsider has posted a nice roundup of the Maps improvements in GM including smoother borders around foliage and "leaf-level" detail. Rather than dealing with privacy issues presented by people and cars, Apple uses a slick algorithm that automatically removes cars and from its map flyovers. (Google blurs faces and license plates.)
This MacRumors forum thread is tracking other changes in the iOS 6 GM, including:
Wifi+Cellular Removed from settings
A few new wallpaper added since beta 4
Panorama mode added to the iPhone 4S in camera app
Many cities now supported in 3D on maps application
Option added to "About" to limit ad tracking
You can now have the first page of the springboard completely empty (All iOS Devices)
The corresponding Xcode 4.5 GM seed is now available as well.