I spent last week at Microsoft's Worldwide Partner Conference, with 16,000 of the company's 460,000 partners, and Windows 8 was at the top of the agenda. My recent experience using a Samsung Series 7 running Windows 8 has convinced me this is a potential game-changing moment for Microsoft and the industry--rivaling even the original Windows 3 launch (which I attended way back in May, 1990).

Before the game really changes, however, especially for the enterprise, Microsoft needs to show the world what the new game looks like and what the rules of engagement will be. We got inklings of that in the keynotes by Tami Reller and Kirill Tartarinov, the heads of Windows and Dynamics, respectively, but inklings aren't enough. In order to drive the market towards a vision of Windows 8 in the enterprise, Microsoft will have to come up with some killer apps that leverage the potential of Windows 8, Dynamics, Azure, and the rest of the Microsoft stack.

It's an unprecedented opportunity, and missing it isn't an option. Microsoft is poised to drive a reimagining of the PC, tablet, and phone user experiences that could completely upturn a tablet market that Apple defined scarcely two years old. And essential to that reimagining is showing how users--and developers--should look at the interplay between these three device types.

The opportunity to blend PCs, tablets, and phones is unique to Windows 8: Apple has MacOS for PCs and iOS for tablets and phones; and Google has Android for tablets and phones, and basically relies on browsers to deliver its desktop user experience, such as it is.

But Windows' uniqueness can't and won't last long. It's hard to imagine twelve months going by without Apple trying to merge its three platforms in some way or another, particularly if Windows 8 shows signs of success. I have less confidence in Google mounting a response--its enterprise chops are pretty much non-existent, as far as I can tell, as witnessed by Google's inability to grok the need for enterprise-class security in Android devices.

[ Want more on Windows 8? Read Microsoft Must Get The Windows 8 Commerce Model Right. ]

Regardless, the challenge on the table for Microsoft is important. Underlying the need for a killer demo app is the need to impress upon the company's millions of developers, plenty of whom already moonlight developing in the iOS market, that Windows 8 is worthy of their attention. The OS has to overcome the unmitigated disaster called Windows 6 phone and its follow-up, a Windows 7 phone that proved to be another developer dead end. In order to get millions of developers geared up to produce millions of Windows 8 apps, the value add over iOS and Android must be pretty compelling.

Building this killer demo app could be more daunting than it may seem, but that's mostly because of the plethora of compelling concepts and technologies that should be part of the scenario. Conceptually, Windows 8 is really intended to be the first development and deployment environment that spans the phone, tablet, and PC user experience. But there's a twist: Surface. tablets like Series 7, and the many convertible laptop/tablets about to enter the market are breaking down the artificial barrier between tablets and PCs that Apple created with iPad.

Whereas iPad is primarily a consumption device, with what amounts to some elegant kludges for enabling varying degrees of input, the Windows 8 tablet experience will be for both creation and consumption. With many new hardware devices either coming with a built-in keyboard (like Surface and the convertible laptops) or supporting a variety of Bluetooth keyboards (like Series 7 and its brethren), the line between tablet and PC begins to blur.

Which means the two distinct user experiences that characterize these devices--keyboard and mouse input on the PC and multitouch input on the tablet--will converge in some, if not all, Windows 8 apps. From a design standpoint that's more complex than it may seem: Not only can you add a keyboard and mouse to Windows 8 apps, but Windows 8 lets you extend the screen options so that you can have a pure keyboard and mouse (no touch) experience on a monitor, and pure touch or touch plus keyboard and mouse on the tablet.

These multi-input, multiscreen capabilities greatly extend what an app can look like and do in Windows 8. Could an app have touch, keyboard, and mouse as its primary input technologies, depending on the particular use case? Why not? Imagine an asset management app that spanned the parts of the process that take place in the field (inspection, verification, inventory control, and service, for example) and at the user's desk (dispatch, verification, field service, and approvals) The same user could take his or her Surface into the field, inspect and verify using a tablet UI, and then flip open the keyboard and write a detailed report . That report could then be presented in a touch-based presentation mode or modified for collaboration with different user input modes depending on whether collaborators are at their desks, in front of a tablet, or on a Windows phone.

In other words, the distinctions between what happens in "mobile mode" and what happens in "desktop mode" can be part of the same app, and have a similar and overlapping user experience. This essentially offers the possibility of extending how much of the scope of a business process can be covered by an app: Business processes that have gone mobile typically have separate mobile modes that are significantly different from their desktop modes, and in most cases the two modes are covered by different apps with different user experiences and licenses. (The situation is different with a pure consumption app like a dashboard or standalone analytic. The visualization of information can be largely the same for all three devices. It's input and interaction that require different approaches.)