(Please note: All the features were from the Apple Support site).
Improves reliability of Address Book syncing with iPhone and other devices and applications.
Improves the reliability of AirPort connections, including improvements when roaming in large wireless networks with an Intel-based Mac.
Improves reliability of synchronizing files on a portable home directory. Fixes an issue in Mac OS X 10.5.4 and 10.5.5 in which managed users may not see printers that use the Generic PPD. Client computers that use UUID-based ByHost preferences now respect managed Screen Saver settings.
Addresses an issue that could cause an encryption alert to appear in the chat window. Setting your iChat status to "invisible" via AppleScript no longer logs you out of iChat. Resolves an issue in which pasting text from a Microsoft Office document could insert an image rather than text.
Includes general improvements to gaming performance. Includes graphics improvements for iChat, Cover Flow, Aperture, and iTunes. Includes fixes for possible graphics distortion issues with certain ATI graphics cards.
Includes overall performance and reliability fixes. Improves Connection Doctor accuracy. Fixes an issue that could cause messages identified as junk to remain in the inbox. Fixes an issue that could cause Mail to append a character to the file extension of an attachment. Addresses an issue that could prevent Mail from quitting. Improves reliability when printing PDF attachments.
Contacts, calendars, and bookmarks on a Mac automatically sync within a minute of the change being made on the computer, another device, or the web at me.com.
Improves Apple File Service performance, especially when using a home directory hosted on an AFP server. Important: If you are using Mac OS X 10.5.6 (client) to connect to a Mac OS X Server 10.4-based server, it is strongly recommended that you update the server to Mac OS X Server version 10.4.11. Improves the performance and reliability of TCP connections. Improves reliability and performance for AT&T 3G cards. Updates the ssh Terminal command for compatibility with more ssh servers.
Improves printing for the Adobe CS3 application suite. Improves printing for USB-based Brother and Canon printers.
Addresses an issue in which a parentally-controlled account could be unable to access the iTunes Store. Includes general fixes for time limits. Resolves an issue that prevented adding allowed websites from Safari via drag and drop.
Fixes issues that could cause Time Machine to state the backup volume could not be found. Improves Time Machine reliability with Time Capsule.
Improves compatibility with web proxy servers.
Includes Mac OS X security improvements. See this website for more information. Addresses inaccuracies with Calculator when the Mac OS X language is set to German or Swiss German. Improves the performance and reliability of Chess. Improves DVD Player performance and reliability. Performance improvements for iCal are included. Fixes an issue when running the New iCal Events Automator action as an applet. Adds a Trackpad System Preference pane for portable Macs. Improves compatibility with smart cards such as the U.S. Department of Defense Common Access Card. Updates time zone data and Daylight Saving Time rules for several countries.