Earlier this week, Microsoft formally introduced Windows 8 to its developer community at its Build conference. The new operating system was well received--so much so that Microsoft CEO Steve Ballmer had to caution people who downloaded the developer preview version that it's very early software and should in no way be used for production environments. Windows 8 is, in a way, Microsoft's answer to both iOS and OSX from Apple: It will run on PCs, notebooks and netbooks, like Windows 7, but it will also run on tablets, like iOS. It'll run on Intel processors like Windows 7, but it will also run on ARM processors like iOS. It runs all the Win32 desktop-style applications that Windows 7 does, but it also has a touch-oriented user interface and supports touch-based applications like iOS.
Windows 8's "secret sauce" is a new touch-oriented user interface called Metro. Metro is based on the Windows Mobile 7 operating system's user interface for smartphones, which is in turn based on the now-defunct Zune user interface. It does the sliding, zooming and selecting kinds of things that you'd expect from iOS and Android, but it does it on top of Windows. That represents both an opportunity and a problem.
The opportunity is that one operating system, Windows 8, could service both the legacy PC market and the new tablet market. Most observers believe that Apple will eventually unify iOS and OSX; Microsoft has done it with Windows 8. It's much easier for developers to build and support applications for one operating system instead of two.
Windows 8 supports two different kinds of applications: Win32 and Metro-style. Win32 applications are the programs and user interface elements that we've seen on Windows since Windows 3.1. They've been refined and updated over the years, but a Windows XP user shouldn't have any difficulty using a Win32-style program on Windows 8. Win32 apps are designed for a keyboard and mouse, and will work poorly, or not at all, with a touch interface. Metro-style applications, on the other hand, are all full-screen, use a radically different user interface, and are optimized for touch. You can use a mouse and a keyboard with Metro-style apps, but you probably won't want to do so.
Windows 8 systems will open into the Metro user interface, using a touchscreen. If you want to run a Win32 app, you'll switch back to the old user interface, using a keyboard and mouse. You'll then go back and forth between user interfaces as you switch from program to program. You can configure Windows 8 to always use a Win32-style GUI, but then you'll lose access to the Metro-style apps. That's the problem with running both Win32 and Metro-style applications on the same device.
Apple knew that tablets were going to be used very differently from desktop computers, so it optimized iOS for touch on smartphones and tablets. iOS doesn't try to run OSX-style keyboard-and-mouse applications; it offers similar functionality, but the user interfaces are very different. Windows 8, on the other hand, wants to be equally good at desktop and tablet applications, even though the use cases are very different.
For existing Windows users who want to continue using Win32-style apps, from what Microsoft showed this week, there's not much value in upgrading to Windows 8, other than cutting down on boot times. Customers who are primarily interested in Metro-style tablet apps will find that app developers are starting from scratch, and it may take years for Microsoft to reach parity with the selection in Apple's iOS App Store. Customers who want to use both types of apps, and switch back and forth, are likely to get frustrated very quickly with dealing with two dramatically different user interfaces.
My suspicion, sitting a year or more away from when Windows 8 formally launches, is that Metro-style apps will be used almost exclusively on tablets, and that desktops, notebooks and netbooks will almost exclusively be used for Win32-style apps, despite Microsoft's goal of getting touch-enabled displays on every kind of computing device. This approach will allow customers to avoid switching between user interfaces, but it won't do much for Microsoft's growth prospects. Windows 8 on conventional PCs and Windows 8 on tablets will represent two different markets, and on the tablet side, Microsoft won't be able to leverage its huge PC installed base. It'll be starting from zero. Given that Apple will probably be on the iPad 4 and Google will be on Android 5 by the time that Windows 8 ships, that's not a good place for Microsoft to be.