As of press time, the 321MB update was only available via the Software Update mechanism located under the Apple menu of your Mac.
In addition to general stability improvements and over two dozen security enhancements, the update addresses issues with Address Book, Disk Utility, iCal, Mail, MobileMe, and Time Machine. A detailed list of those fixes follows:
- Includes recent Apple security updates.
- Addresses stability issues with video playback, processor core idling, and remote disc sharing for MacBook Air.
- Addresses an issue in which some Macs could unexpectedly power on at the same time each day.
- Resolves a stability issue in TextEdit that could be found when accessing the color palette.
- Improves Spotlight indexing performance.
- Fixes an issue in which contacts might not sync properly with PalmOS-based devices.
- Improves iPhone sync reliability with iCal and Address Book.
- Includes improvements to Active Directory (see this article for more information).
- Improves Speech Dictionary.
- Fixes Kerberos authentication issues for Mac OS X 10.5 clients that connect to certain Samba servers, such as Mac OS X Server version 10.4.
- Includes extensive graphics enhancements.
- Addresses stability issues that may occur when creating a Smart Group.
- Resolves a printing issue with address cards containing information that spans more than one page.
Disk Utility and Directory Utility
- Improves reliability when rebuilding a software mirror RAID volume in Disk Utility.
- Improves reliability of server status displayed in Directory Utility.
- Updates iCal to more accurately handle repeating events.
- Improves performance when choosing meeting attendees.
- Resolves an issue in which the "Refresh All" option may be dimmed ("grayed out") in the contextual menu for certain calendars.
- Fixes issues with read-only calendars.
- Addresses an issue that prevents an invitee from moving an event to a different calendar.
- Resolves an issue with syncing published calendars.
- Addresses performance issues related to displaying IMAP messages.
- Resolves an issue with SMTP settings for AIM, Compuserve, Hanmail, Yahoo!, and Time Warner Road Runner email accounts.
- Addresses stability issues that may occur when dragging a file to the Mail icon in the Dock.
- Addresses an issue with the "Organized by Thread" view in which the date does not appear when the thread is collapsed.
- Resolves an issue in which RSS feeds could temporarily disappear from the sidebar.
- Improves Mail robustness when sending messages.
- Improves reliability when saving drafts that have attachments.
- Improves overall sync reliability.
- Improves Back to My Mac reliability.
- Improves Time Machine reliability with Time Capsule.
- Addresses performance issues that may affect initial and in-progress backups.
- Fixes an issue in which an incorrect alert message could appear stating that a backup volume does not have enough free space.
- Time Machine can now back up iPhone backups that are on your Mac, as well as other items in (~/Library/Application Support).
On September 5th, AppleInsider cited sources who said Mac OS X 10.5.5 was only a week or two away.