Headline pretty much says it all, and it's a big one. Tipping the scales at 377MB (or 190MB for some; see image after the break), the OS X 10.5.6 update is now available via Software Update. We're sucking it down and will report back with any changes. We strongly encourage you to do the same (if you dare).
Update: Apple has posted the official changelog. Here are the highlights:
Improves the reliability of AirPort connections, including improvements when roaming in large wireless networks with an Intel-based Mac.
Improves reliability of Address Book syncing with iPhone and other devices and applications.
Includes general improvements to gaming performance.
Includes fixes for possible graphics distortion issues with certain ATI graphics cards.
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.
Improves reliability and performance for AT&T 3G cards.
Improves printing for USB-based Brother and Canon printers.
Fixes issues that could cause Time Machine to state the backup volume could not be found.
Improves Time Machine reliability with Time Capsule.
Adds a Trackpad System Preference pane for portable Macs.
Personal Engadget favorite: Improves the performance and reliability of Chess.
Nary a mention of Blu-ray. It's still hurting, we guess.