updated 09:00 pm EDT, Mon September 16, 2013
New Safari 6.1 beta has also been released for Lion, Mountain Lion
[Update: more details added, including iTunes 11.1] A day early, Apple has seeded another "Developer Preview" of OS X 10.9 Mavericks, two weeks after the previous release. Registered developers can obtain the new version by signing into the Mac App Store with their developer account Apple IDs. In addition, Apple released a new Safari 6.1 beta for Lion and Mountain Lion, as well as an updated build of iTunes 11.1. Mavericks DP7 also continues to list iCloud Keychain as an area for testing, with several bugs still existing in its implementation. Current speculation has Mavericks on track to be released alongside updated Mac models sometime in mid to late October.
While the version of Safari in OS X Mavericks will be numbered 7.0, many of the improvements are being handed down to Safari 6.1 for the two most recent OS versions, signalling that Apple will formally drop support for Snow Leopard (10.6.x) once Mavericks is released, in keeping with its usual practice. A number of the features in Safari 6.1 will be available only to Mountain Lion users, encouraging Lion users to migrate forward.
The release notes for the eighth Mavericks Developer Preview include the fact that network migration from earlier versions of OS X requires the Migration Update for Snow Leopard, Lion or Mountain Lion -- while migration from Windows requires the Windows Migration Assistant 220.127.116.11, both of which are available from the Mac Dev Center. Also included in the new version is an updated build of iTunes 11.1 (build 110, versus the build 48 that is still available on the Mac Dev Center).
An issue where purchased music may not show cover art in Preview is also noted. To resolve it, Apple suggests a working around involving running the command glmanage -r cache in Terminal.
The public release of Mavericks will feature Maps for OS X, iBooks for OS X, Finder Tabs and other efficiency features such as Compressed Memory and App Nap, which should enhance power savings in the company's MacBook line in addition to savings coming from the updated Intel Haswell chip.. To that end, conventional wisdom has it that Apple will hold back updated MacBook Pro models (and possibly other Mac models) until sometime in October, when Mavericks is expected to leave beta and be publicly released.