According to people familiar with the latest version of Mavericks, the new build shows no major changes, likely meaning only minor bug fixes and performance tweaks were made in the two weeks since the second developer preview was seeded in June. Apple has been on a two-week release cycle for both Mavericks and iOS 7 betas, the latter being seeded earlier on Monday.
The accompanying release notes suggest changes have been made to how Mavericks handles the forthcoming iCloud Keychain feature, as the seed is not backward compatible with iOS 7 Seed 2 or Mavericks Developer Seed 2. As such, users will need to re-enable iCloud Keychain from the iCloud preferences pane after upgrading to Developer Preview 3.
Other known issues include graphics problems when resizing or switching from standard to satellite view in Maps, file handling in Aperture and Photoshop, and various small bugs. Finally, the notes point out that Fusion Drive volumes created in Developer Preview 3 are incompatible with OS X 10.8.4 or earlier.
When Mavericks launches this fall, it will bring a number of improvements and feature additions to the current OS X 10.8 Mountain Lion, including Finder tabs, Maps, App Nap and Compressed Memory, among others.
Developers can download the the third Mavericks preview via the Mac App Store.