Apple has released OS X 10.11 El Capitan GM release to developers. It is now available for developers who are registered with Apple Developer Program. The new build golden master number is 15A282b and it is the last release before the public availability on September 30.
OS X 10.11 El Capitan features improved performance, better battery life, new split screen apps usage, enhanced Mission Control along with improvements and new features for Mail, Safari, Notes and much more. Having used the beta for a while now on a 2013 MacBook Air, I can confirm that this release is worth the update and addresses most complaints that users had with OS X 10.10 Yosemite. However, many old iMac users have not been too happy with the betas so it is yet to be seen whether the GM or public release fix their concerns or not.
OS X 10.11 GM build will not be available as an OTA update via Mac App Store for existing developer beta and public beta users. If you download the GM seed, you would have download the installer and do an upgrade manually.
September 9 event day has been busy for Apple. Along with the announcements for iPad Pro, Apple TV, Apple Watch and iPhone 6s, software updates have gone out for all its operating systems including WatchOS 2 GM and iOS 9 GM whereas a new iOS 9.1 beta has also been released today.
If you are registered with Apple Developer Program, you can go ahead and download OS X El Capitan 10.11 GM release right now.