It took 11 months, but Microsoft's Windows 8 has passed Apple's OS X in market share, according to StatCounter.

StatCounter's numbers for September show 7.46 percent market share for Windows 8, an increase of 0.44 percent over the previous month. That was enough to surpass Mac market share, which dropped 0.2 percentage points to 6.98 percent.

See that tangled mess of colored lines at the bottom? Windows 8 and OS X are slugging it out in there, while Windows 7 and XP are the clear OS leaders. (Click to enlarge.)

Meanwhile, older versions of Windows are holding somewhat steady. Windows 7 saw a 0.03 drop to 51.98 percent share, Windows XP rose by 0.01 points to 20.59 percent and Windows Vista somehow gained 0.09 points, bringing it to 5.3 percent market share. So while Windows 8's market share is steadily rising, previous versions aren't going away.

NetMarketShare's September usage stats. (Click to enlarge.)

If this news sounds familiar, it's because last month, rival measurement firm NetMarketShare found that Windows 8 market share had cruised past OS X in August. That trend continued in September, with Windows 8 rising to 8.02 percent, compared to 7.54 percent for OS X.

StatCounter and NetMarketShare use different methodologies, but both firms get their data by measuring traffic on a sampling of large websites—and both now place Windows 8 usage ahead of all versions of OS X combined.

Upgrade blues

Worth noting, however, is that nearly half of Mac owners are using the latest version of OS X, called Mountain Lion, according to NetMarketShare. Apple's strategy of charging just $20 for OS upgrades is clearly paying off. The vast majority of PC users are still rocking older version of Windows, even though Microsoft originally charged just $40 for Windows 8 Pro upgrades before raising the price to $120 for Windows 8 and $200 for Windows 8 Pro.

While the rising share of Windows 8 should be somewhat encouraging for Microsoft, the greater health of the PC industry is still in jeopardy. Worldwide PC sales are falling, and back-to-school sales in the United States dropped by 2.4 percent this year according to The NPD Group, as people turn to tablets instead of basic $500 laptops. The way forward for PC makers may be not in raw market share, but in high-end Windows machines priced over $700, whose back-to-school sales actually rose 24 percent this year, along with cheaper touch screen devices. Both categories could help Windows 8 grow, even as some users stay attached to their Windows 7 and Windows XP workhorses.