No one is unhappy with Mac OS X Version 10.4, known as Tiger. OS X is not an application platform (I bristle at using the term "operating system" for OS X; I explain why below) that needed repair, speeding up, or exterior renovation. Motivations for major upgrades of competing system software — roll-ups of an unmanageable number of fixes, because the calendar says it's time, or because users are perceived to have version fatigue — don't apply to OS X. Apple wields no whip to force upgrades because Tiger stands no risk of being neglected by Apple or third-party developers as long as Leopard lives. Despite the absence of a stick that drives users into upgrades of competing OSes, or perhaps because of it, Apple enjoys an extraordinary rate of voluntary OS X upgrades among desktop and notebook users. Why? People buy Macs because the platform as a whole is perfect, full stop. Leopard is a rung above perfection. It's taken as rote that the Mac blows away PC users' expectations. Leopard blows away Mac users' expectations, and that's saying a great deal.

The Bottom Line Mac OS X 10.5 (Leopard) Apple, apple.com Excellent  10.0 criteria score weight Ease-of-use 10 20% Compatibility 10 20% Management 10 20% Features 10 15% Security 10 15% Value 10 10% Cost: $129 Platforms: Macs with an Intel, PowerPC G5, or PowerPC G4 (867MHz or faster) processor Bottom Line: Apple's latest Mac platform software, released simultaneously for Intel and PowerPC-based Macs, marks a turning point for the Mac. Leopard users and developers immediately reap the benefits of Leopard's greatly enhanced Mac frameworks. Almost nothing is buried for Apple or developers to uncover, while users gain from Apple's unsurpassed attention to usability and effortless integration from stem to stern. Leopard will change the way you work with computers, and entirely for the better. About our Reviews and Scoring Methodology

[ Leopard was selected to receive an InfoWorld Technology of the Year award. See the slideshow of all the winners in the platforms category. ]

Apple's secret, which is no secret to Mac users, is that major OS X releases deliver tangible value far in excess of their asking price, which in Leopard's case is $129. OS X is, first and foremost, a platform for integrated, user-facing applications. And to a far greater extent than previous releases, OS X Leopard itself exploits the facilities that Apple's developers have used to create the vendor's commercial software. Apple hasn't reserved any of the Mac platform's goodies for itself, and users don't need to wait (or spend) for apps that expose the platform's richness in productive ways.

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For example, Screen Sharing is now built into OS X; just open the Finder icon for a remote server and click the Screen Sharing button to grab the remote system's display and, optionally, its mouse and keyboard. Apple built Screen Sharing into iChat, and Back to My Mac uses the .Mac service and Screen Sharing to securely tunnel to files and consoles on Macs behind firewalls. All of Leopard is like that — every Leopard feature, even those that would ordinarily be invisible to all but developers, or reserved for the use of the vendor, is planted throughout OS X in the places you'd put it.

Freedom in the frameworks
Looking at it from a technical perspective, Leopard's step past perfection lies in its extensive use of the combination of the Mac platform's intrinsic integration and Leopard's delivery of hundreds of additions and enhancements to OS X's frameworks.

Apple supplies a consistent, familiar, and well-documented path for developers to do any given thing. In contrast, an entire industry has sprung up around providing developers with proprietary plugs for the gaps that Microsoft leaves in Windows, often intentionally as an aid to the third-party development community. The completeness of the Mac frameworks leaves no room for a marketplace for Mac developer library enhancements.

What's changed in Leopard is that Apple has invested enormous effort to expose Mac framework enhancements to users through OS X's built-in facilities and applications. Leopard's out-of-the-box experience, which I define as the things that a user can do without spending an extra dollar on software, eclipses Tiger's, and Tiger was no slouch in this regard. In the past, third parties have offered freeware and shareware facilities to extend or even replace Finder, the Mac's answer to Windows' primitive Explorer. That died out with Tiger, and Leopard makes such efforts entirely useless. That is not a bad thing.