The above graph shows the OS stats for W3C since March, 2003. Side-stepping the debate over whether the stats are an accurate representation of the OS share, I'd like to look at the trends the graph shows (which I believe to be accurate) and what it means for Linux-based OSes.
The most obvious line on the graph is XP's. That's no surprise. It peaked at the beginning of 2007 and began a slow decline from there. Not coincidentally, Vista was released in early 2007. XP showed a later bump which some might attribute to Vista, but I believe those numbers came from the losses in Win2000. From that point on, Vista climbed while XP and 2000 fell off. I think most would agree that represents the reallity of the OS market.
More interesting stuff happens at the bottom of the graph. If you can tell, Linux ranks above Mac until 2006, when they each sit at about 3.5%. After 2006, both OSes grow steadily with OS X ending at 6% while Linux is at 4%. Clearly, OS X has the momentum.
What about Windows users as a whole? In 2003, the share was 93%, trending down to below 87% in 2008, then recovering to over 90% again. If I were able to get earlier numbers for Windows, I would guess that it would have sat at 97-98% during the late 90s. In other words, that line would keep its slope through the previous few years.
The enigmatic "Other" OS rose to over 5% during Windows' slump, then crashing to well under 1%. Although I can't accurately guess what the "Other" OS is made of (maybe smart phones?), the 5% of its users fled and about half went to Windows , 30% to Mac, and 20% to Linux.
My analysis? Although you see a recent bump in the Windows numbers, that is probably due to a change in the way W3C categorizes "Other." Both Linux and Mac are moving slowly up the graph at the expense of Windows. My prediction? Mac will see another 2% growth year -- getting it over 8% -- while Linux will rise .25-.50% in 2009, leaving it sitting firmly in the over-4% range in 2010.