Computerworld - Five months after its release, Apple's Mountain Lion became the most widely-used version of OS X, a Web measurement firm said Tuesday.
According to California-based Net Applications, OS X 10.8, better known as Mountain Lion, accounted for 32%, or nearly a third, of all Macs that went online during December. That was an increase of nearly three percentage points from November, when Mountain Lion powered just over 29% of all Macs.
Apple released Mountain Lion on July 25, 2012.
Most of Mountain Lion's gains came at the expense of OS X 10.7, or Lion, whose share of all Macs dropped from 30% to 28%. Snow Leopard lost less than one percentage point in December, a smaller-than-usual decline for the 2009 OS X 10.6, which in the last year has averaged a drop of about one-and-a-half points each month.
Snow Leopard has shown such strong staying power that Computerworld has compared it to Microsoft's Windows XP, an 11-year-old operating system that stubbornly refuses to go quietly into the night.
As of Dec. 31, OS X 10.6 was the second-most-used Mac operating system, with an online usage share of 29%, said Net Applications.
While Snow Leopard users have cited a variety of reasons for sticking with the operating system, the most mentioned is its ability to run applications developed for the PowerPC processor, the CPU co-designed by Apple, IBM and Motorola, and used by Macs before Apple switched to Intel processors in January 2006.
Snow Leopard was the last version of OS X to let users run PowerPC applications, even though it runs only on Intel-based Macs.
Mountain Lion's rapid adoption wasn't unusual: OS X 10.8's uptake trajectory continued to mirror that of Lion and to a lesser degree, Snow Leopard, during December. Historically, Apple has had much better luck getting its customers to upgrade to new operating systems than has Microsoft, whose Windows is at a disadvantage because of its enormous user base and importance to businesses, which are much more conservative about upgrading than consumers, where Apple is strongest.
Although current projections based on the uptake average of the last three months indicates Mountain Lion should crack the 50% mark in April, that's unlikely. Lion, for example, peaked at 47% in July 2012, a year after its release.
One factor that will limit Mountain Lion's eventual top mark was Apple's announcement last February that OS X would adopt an annual release cycle, meaning that, like Lion last summer, Mountain Lion will soon be superseded by something newer, probably this summer.
Microsoft has reportedly also assumed an annual release schedule for Windows, with the first instance of that express cycle slated to ship around the middle of this year.
Net Applications measures operating system usage by tracking unique visitors to approximately 40,000 Web sites. More information about its December statistics can be found on the company's website.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at 
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