Prior to the Windows 8 launch last fall, Microsoft had a strong belief that it was going to change the computing world forever. Instead, it became one of the worst-received OSes the company had ever pushed out. I'd bring up the definitive "worst", but I fear for reoccurring nightmares.
Still, while much of the world continues to scoff at the idea of using Windows 8, Microsoft has gained itself a bit of a right to gloat: The OS has seen a constant increase in usage since its release. To be fair, a lot of this increase owes its thanks to OEM builders, but even so, the fact that most people are not backtracking to Windows 7 should prove that Windows 8 isn't as bad as a lot of people make it out to be.
According to Net Applications, a firm that gathers its data from a large number of the world's biggest websites, Windows 8's overall marketshare increased from 5.1% in June to 9.3% in November. That's a far cry from Windows 7's market-leading 46.64%, but given the flak Windows 8 has received since its launch, the numbers could be much worse. Plus, let's not ignore the fact that a lot of Windows 7 users consider it to be the "perfect" OS, so the need to upgrade would feel nonexistent - no one likes spending money just for the sake of it.
When singling Windows 8.1 out, November saw its usage surpass Mac OS X 10.9 - 2.64% vs. 2.42%. There are a couple of things that makes this notable: Both were released 100% cost-free (to owners of the previous version), and both were released 5 days apart. That said, given Windows 8 had already surpassed OS X as a whole a couple of months ago, this overtake was inevitable.
For the Linux fan, the above pie chart might come off as a bit depressing, but month-over-month, its dropping off and coming back seems to be typical. Still, at a current 1.56% usage share, it's a relative runt to the other OSes.
As we're in the midst of the annual mega-buying season, it will be interesting to see how these charts will change over the next couple of months.