According to people familiar with the release notes, build number 12E27 doesn't show any changes in the areas on which developers should focus, suggesting the software contains bug fixes and small enhancements at this time.
Like the final OS X 10.8.3 betas, the first 10.8.4 seed asks testers to look at Wi-Fi, Graphics Drivers and Safari, while the seed comes with no known issues.
Interestingly, Apple said it is not offering the build as a software update through the Mac App Store, as it did with the 10.8.3 builds. This may change with future seeds, but the company didn't elaborate further.
The new seed come a over two weeks after Apple released OS X 10.8.3 to the public with Safari 6.0.3 and enhanced iTunes integration. Along with the new feature set, 10.8.3 brought bug fixes and wider support for Windows 8 in Boot Camp.