Apple keeps on improving is Leopard operating system at a serious pace. The company released Mac OS X 10.5.4 today, with the standard blurb attached to it: “The Mac OS X 10.5.4 Update is recommended for Mac OS X 10.5, 10.5.1, 10.5.2, and 10.5.3 Leopard. It includes general operating system improvements that enhance the stability, compatibility, and security of your Mac. “ The update includes fixes concerning AirPort, iCal, Safari, Spaces, and Expose. Software Update will bug you with the new release, or you can just start the updater yourself.