Similar to OS X El Capitan Beta 8, the GM build of OS X El Capitan is a minor update featuring enhancement to the operating system, under-the-hood performance improvements, as well as bug fixes. Although OS X El Capitan GM, the golden master edition of OS X El Capitan, is considered the final build and will most likely be identical to the one that will be released to the public.
OS X El Capitan GM is now available to download through Software Update or via the Mac Dev Center for registered developers.