By CEO Steve Ballmer's own description it is the one of the top three major events in the company's history, grouped with IBM PCs adopting MS-DOS and the advent of Windows 95.
By that measure, if it's a flop it's huge.
Windows 8 drives users crazy. It's a two-headed operating system that supports the traditional Windows keyboard-and-mouse interface as well as a touch-centric UI that many say is baffling, at least initially.
Then toss in a separate version of Windows 8 called Windows RT. It's a hardware/software bundle based on ARM processors that doesn't support traditional Windows x86 apps -- only so-called Windows Store applications that rely mainly on touch. Confusion reigns.
A version of the traditional desktop remains in Windows 8, but it's different enough to be uncomfortable. Users want an OS that builds on the past, not one that reinvents itself entirely. They lament the loss of the Start button and Start Menu upon which they relied.
When learning the Windows 8 touch interface they find it difficult to find and remember, say, how to turn the machine on and off, close applications, remove applications, switch among four or five apps running at the same time, find Charms, figure out what Charms are, etc., etc. It's a near-perfect storm of consternation and frustration.
Meanwhile the company's traditional PC market is being threatened by devices running Linux, Android and OS X even as sales growth of traditional PCs gets slower and slower, apparently headed for decline. That's Microsoft's bread and butter.
Compounding the problem, tablets and smartphones are gaining popularity as personal and business productivity platforms and arguably represent the main force undercutting traditional PCs. Microsoft comes in a distant third in both areas.
Windows 8 is supposed to help Microsoft make gains in these areas. But given its slow start so far and comparing it to the wild success of every version of iPad that ever launched, then Windows 8 is lining up to be a disaster.
So what was Microsoft thinking?
Windows 8 is designed to tap into the shift in demand away from traditional desktops and laptops and toward phones and tablets.
Core to this strategy is making a shift to mobility and creating an application environment transferrable from device to device. The advantage: Massive blocks of code from an application written for Windows 8 can be readily repurposed for apps written or Windows Phone 8 -- making it feasible for these apps to be available on any Windows device.
Because Windows Store apps are written primarily for touch, their navigation is similar from tablet to notebook to phone. Applications are available for phones, tablets and laptops, and if you master them on one category of device, you've mastered them for all.
These applications, called Windows Store apps, represent a new category optimized for touch and for running on lower powered mobile machines based on ARM processors to promote longer battery life.
In addition, Windows 8 heavily promotes use of cloud services. It comes with cloud-based music free and integrates SkyDrive, Microsoft's 5-year-old cloud storage service that enables sharing data among devices and syncing them with each other. It comes with 7GB of free storage.
The bottom line is customers can access the latest versions of their data and all their stored files from whichever device they happen to have with them so long as they have Internet access.
The problem is that this elegant scheme is lost on customers, analysts and reviewers who don't buy into this view. With education, customers could be won over, but not in the short-term, and particularly with RT. Business customers will have to adopt Windows Store apps or virtualize, and that takes time.
"It will take 10 or more years before most organizations completely transition to WinRT technology, which, if successful, will represent the next 20 to 30 years of Windows," says Gartner in its report "Windows 8 Changes Windows as We Know It."
Beyond Windows 8, Microsoft has scored some hits and some misses this year with new products acquisitions. Here are four of each.