If online pre-sales are any indication, Apple's new Snow Leopard operating system should be a big hit.

Within hours of Apple's announcement that Snow Leopard, aka Mac OS X 10.6, hits stores and e-commerce sites Friday, the operating system became the stop seller in Amazon.com's software category, according to the Web retailer's Sales Rank page.

Adding to Cupertino's presumed satisfaction is the fact that Snow Leopard ousted Microsoft Office 2007 from Amazon's top spot.

Further bolstering optimism around Snow Leopard, a financial analyst on Monday predicted big sales for the OS. Piper Jaffray's Gene Munster said he expects Apple to sell 5 million copies of Mac OS X 10.6 through the end of the current quarter. Mac OS X 10.5 Leopard users can upgrade to the new version for just $29.

Munster also said Snow Leopard could help Apple make inroads against Microsoft in the OS market, with Redmond not expected to release Windows 7 until Oct. 22nd.

"Apple is promoting the Mac platform as a superior alternative to Windows in terms of newer technology, more frequently, for less money," Munster wrote in a research note. "The release of Snow Leopard is not about new features; rather, it is about keeping Mac users up to date with the latest technology vs. Windows XP and Vista users on antiquated technology," the analyst said.

Snow Leopard introduces a number of new features to the Mac operating environment, particularly for power users.

"For the first time, system applications including Finder, Mail, iCal', iChat' and Safari are 64-bit and Snow Leopard's support for 64-bit processors makes use of large amounts of RAM, increases performance and improves security while remaining compatible with 32-bit applications," Apple said in a statement.

Mac OS X 10.6 also includes a new multithreading technology that should prove popular with gamers and other users that require maximum horsepower for graphics processing and other computationally intensive tasks.

"Grand Central Dispatch (GCD) provides a revolutionary new way for software developers to write applications that take advantage of multicore processors. OpenCL, a C-based open standard, allows developers to tap the incredible power of the graphics processing unit for tasks that go beyond graphics," Apple said.

Snow Leopard also offers built-in support for Microsoft Exchange Server 2007, a feature that could help Apple make gains in the enterprise and small business markets.

In addition to the single-user, $29 upgrade license, Apple is offering a $49 Snow Leopard Family Pack that allows five installations per household.