Apple Inc.'s delayed update to the Mac OS X operating system is hitting store shelves as consumers are increasingly snapping up Macintosh computers to complement their iPods and iPhones.

Dubbed Leopard, the upgrade went on sale at 6 p.m. local time Friday at stores around the world. It offers improvements to an operating system that already was widely praised for its ease-of-use and slick interface.

Leopard boasts more than 300 new features, including one called "Boot Camp" that lets users install Windows on Macs, though both operating systems can't run at the same time.

"Time Machine," an automated data backup system, and "Spaces," a way to simultaneously view open applications, are among the other highlighted features.

Macs have reached record sale levels, and the launch of Leopard is expected to bolster a continuing rise.

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At Apple's flagship 5th Avenue store in New York City, a line of about 500 people snaked around the block before Leopard went on sale. The anxious, some of whom queued up more than four hours beforehand, included not only the longtime Apple faithful but new converts.

Patrick van Rosendaal, 31, visiting from Columbus, Ohio, stood in line for an hour and a half before he got his hands on a shrink-wrapped copy of Leopard. He bought his first Mac two months ago.

"Macs are still rather new to me," he said. "But I'm completely addicted."

Dennis Huang, 18, of New York City, was third in line. He became a Mac owner in August after finding the computer "a lot easier to use." While in the store, he was among many giving Leopard's snazzy-looking "Time Machine" feature a whirl.

Computers with Microsoft Corp.'s Windows platform still dominate the PC market, but Apple has made significant gains over the past year, outstripping the worldwide 15 percent growth rate in the rest of the industry.

Apple, which for years hovered at a 2 percent to 3 percent share of the U.S. market, now claims an 8 percent slice, according to market researcher Gartner Inc.

As Apple's iPod players became a cultural phenomenon, they introduced millions of Windows users to Apple's software and design. And the iPhone, Apple's new hybrid cell phone and iPod, is spreading that halo effect.

Also, Apple's 197 shiny retail outlets have become magnets, while Best Buy Co. Inc. started carrying Macs at some of its stores this fall. Apple says more than half of the customers buying computers at Apple stores are new to the Mac platform.

Existing Mac users can buy the Leopard operating system update separately, and it is being built into all new Macs. It costs $129 for a single user or $199 for a license for up to five machines.

Leopard is the sixth major upgrade Apple has made to Mac OS X since the computer operating system debuted in 2001. The previous major upgrade, Tiger, was released in April 2005.

By comparison, it took Microsoft five years to complete its major Windows upgrade, Vista, which went on sale in January and has been since dogged by complaints of incompatibility problems.

Vista comes in different consumer editions, depending how many features are included, and ranges in price from $100 to $400.

Leopard was originally due in June, but Apple said in April it needed to divert resources to accomplish the summer launch of the much-anticipated iPhone and would delay Leopard to do that.

Product delays are rare for the Cupertino-based company, but Apple CEO Steve Jobs — with his typical hubris — promised it would be worth the wait. Now, consumers get to see for themselves whether it will have been.

"That's a common question, and I think the answer will be an emphatic yes," said Phil Schiller, Apple's senior vice president of worldwide marketing.

Shares of Apple, which have more than doubled since January, were up $1.92, or 1.1 percent, to close at $184.70 Friday.