Apple has seeded the final, Gold Master, build of OS X 10.8 to Mac developers worldwide. It carries no known issues and the release notes ask developers to focus their testing efforts on, graphics, media importing, editing, or viewing, and the reliability and performance of networking. This final developer release posseses a build number of 12A269 with the previous one being 12A526. You can expect the final, public release of Mountain Lion very soon since testing is now complete.
OS X 10.8 Mountain Lion has over 200 new features, will cost $19.99 for Snow Leopard and Lion users, and will release in “mid-July,” according to Apple. It’s unlikely that this final developer build has any major changes, aside from the usual bug fixes, but if you happen to be using it, let us know if there’s anything that’s been significantly overhauled.
Apple also released Xcode 4.4 developer preview 6 to paid developers, continuing support for Mountain Lion. It’s the Gold Master as well, so you should expect a final release of this tool right along with OS X 10.8.