Apple's Mavericks operating system set the OS X early-adoption record last month, with a third of all Macs running the new edition within just weeks of its introduction.
The fast uptake validated Apple's rationale for giving away OS X 10.9, aka Mavericks.
"What's most important to us is seeing the software in the hands of as many Mac users as possible," Craig Federighi, who leads software engineering at Apple, said during an October event where he announced that Mavericks would be free.
"Today, spending hundreds of dollars to get the most out of your computer are gone," Federighi added, taking a shot at rival Microsoft, which charges $199 for its Windows 8 Pro upgrade.
Mac users running 2012's Mountain Lion, 2011's Lion and 2009's Snow Leopard on compatible systems have been able to download Mavericks from the Mac App Store free of charge since Oct. 22.
According to Web analytics company Net Applications, Mavericks' accounted for 32% of all versions of OS X used in November, a record one-month jump of 21 percentage points.
Mavericks' adoption after its first full month of availability was nearly double that of OS X Mountain Lion, the $20 upgrade Apple started selling on July 25, 2012. By the end of its first complete month, Mountain Lion had accumulated a 19% share of all Macs.
Mountain Lion required five months to reach 32%, meaning Mavericks did that in a fourth the time.
The bulk of Mavericks' share came at the expense of Mountain Lion, which plummeted 18 percentage points in November -- another record change for OS X -- to end at 25%. Lion dropped 2.5 points, its largest decline since the release of its successor Mountain Lion, ending the month with an 18% user share of all Macs.
Not surprisingly, Snow Leopard barely budged, losing just half a percentage point in November to slip to 20% of all editions. Users of Snow Leopard have stubbornly resisted upgrade opportunities, in large part because it was the last version of OS X to let them run applications compiled for the PowerPC processor.
Although Rosetta, the translation utility that allows PowerPC software to run on Intel-based Macs, is not installed by default on OS X 10.6, or Snow Leopard, it does automatically install the first time a PowerPC program executes. Lion, Mountain Lion and Mavericks do not support Rosetta, and so are unable to run PowerPC applications.
Although Apple has not trumpeted the number of Mavericks downloads, something it regularly did with past OS X upgrades, the operating system remains the No. 1 free download on the Mac App Store, an indication of its continued popularity.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed . His email address is email@example.com.