When a new OS upgrade costs $29, you can be forgiven for thinking of it as a service pack. Such may appear to be the case with Mac OS X 10.6, aka Snow Leopard, which Apple has positioned as an under-the-hood upgrade whose new capabilities won't be so obvious to users, and thus not worth the usual $129.

I agree with that price assessment (if only Microsoft had made the same judgment about Windows 7), but I don't agree that what Snow Leopard offers resides merely under the hood. Instead, it provides many enhancements and some new features that Mac users of all persuasions will really like. (Note: The $29 upgrade price is for Leopard users; if you have an older Mac OS X version, it'll cost you $169 to upgrade.)

[ Get all the details on the new Mac OS X features in InfoWorld's "What's new in Mac OS X Snow Leopard" slideshow trio: new features for all users, new features for office users, and new features for power users. | Follow InfoWorld's ongoing coverage of Mac OS X Snow Leopard. ]

Much of Snow Leopard's focus has been internal. For example, Apple has revamped the kernel, included apps, and much of the OS itself to be 64-bit (to allow virtual addressable memory of 16 exabytes and physical addressable memory of more than 32GB). But until apps are rewritten for 64-bit and the new Mac models support that kind of memory, there's little immediate benefit -- ditto for multicore enablement in the Grand Central Dispatch engine. But the revamped QuickTime X and Java engines should result in faster processing of streaming media and Java applets (such as on Web sites).

Putting aside these important but long-term changes, here are Snow Leopard's most immediately beneficial new features and enhancements.

1. ActiveSync and Exchange 2007 support
Following in the footsteps of the iPhone, Snow Leopard makes these Microsoft technologies native to the OS. That means Apple's e-mail, calendar, and contacts apps work just peachy with Exchange 2007 server, giving users the same capabilities as Microsoft Entourage but with the better-designed, less-memory-intensive apps -- Mail, iCal, and Address Book -- included in OS X.

2. Exposé integration in the Dock
The Mac OS X Dock makes it easy to access applications, open documents, and common folders, a concept Windows 7 is stealing in its retooled taskbar. Open documents are even more easily accessed in Snow Leopard, thanks to the integration of Exposé. Now when you click and hold an app icon in the Dock, you get preview windows for each of its open documents, allowing you to switch easily among them or to close them, all without having to clutter your screen with document windows. I never cared much for Exposé in its traditional role (providing hot corners and shortcuts to open application windows), but I love the Dock-integrated Exposé functionality that Snow Leopard adds.