"According to the seed-note, the update 'focuses' (if we may call this focusing) on, Active Directory/Directory Services, AirPort, AppKit, Application, Firewall, Audio, Automator, Back To My Mac, Chinese Input Methods, CoreData, CoreFoundation, Dashboard Widgets, Data Detectors, Directory Services, Dock, Finder, Foundation, Grammar Checking, Graphics Drivers, High Level Toolbox, iCal, iChat, iDisk, Keyboard Layouts, Mail, Networking, Parental Controls, Podcast Producer, Printing/CUPS, Quick Look, Rosetta, Safari, SMB, Spotlight, SQLite, Terminal, Time Machine, X11," MacScoop reports.
"This clearly represents by far the most significant revision update Apple has ever made on any of its operating systems with nearly 40 Applications involved and 100 bugs fixed. The only bad news is that the update weights as much as, hold your breathe... over 400MB, a record size which could even grow further in the final build," MacScoop reports."