I spent most of the day yesterday in a room with a bunch of media types getting a pre-briefing on Windows 8. A parade of Microsoft execs walked us through the features they’re excited about--everything from the new UI to the development environment for Windows 8 apps to printer support and enterprise features. After the briefing, I got to spend some quality time with a developer build of the new OS running on a pre-production tablet. The developer build has many of the core Windows 8 apps stripped out--there’s no mail client, no People app, no Picture viewer, etc; but I was able to get a much better idea of how the OS actually runs.

After spending a few hours with it, I’m excited to see more.

Metro is New and Exciting Metaphor for Computing

The Desktop as a metaphor for desktop computers has remained relatively unchanged since the dawn of the graphical user interface. The core idea--a workspace with windows that contain the things you’re working on--has had many new features bolted on to it so that it looks dramatically different, but the core idea hasn’t changed since early versions of Mac OS. Although Windows 8 will include a traditional desktop, the screen you’ll see when you first log onto Windows is entirely new.

Windows 8’s new Start Screen is a full-screen, sized-up version of the Windows Phone 7 Home Screen, populated with tiles filled that display dynamic snippets of information--mostly images and snippets of text, but there are other modes as well. This new full-screen Metro-style menu replaces the Start Menu, at least on the developer build of Windows 8 that we got to try out. Desktop die-hards need not freak out (at least not yet), transitioning between the Start screen and the traditional desktop was seamless.

The tiles on the Start screen essentially replace application icons in the Start Menu or on the Taskbar. When you’re on the Start screen, the tiles are constantly updating and animating. Clicking on most tiles simply launches the app, but you can also create tiles that deep link to a specific part of an app. We saw an example RSS reader app that lets you create tiles for specific RSS feeds and the People app, which lets you make a tile for a specific person. This isn’t a new concept for Windows Phone 7 users, but it’s brand new for the traditional PC.

It’s much too early to say whether reimagining the Start Menu and Desktop is a good idea or not, but it’s an undeniably high-risk endeavor for Microsoft. The new Metro-style apps ditch the window--they’re either full screen or split screen--and must be designed to use new software interfaces. Legacy apps will just shell out to the old-school Desktop. It seems like Microsoft has gone to great lengths to make Metro apps easy to build, but if developers don’t embrace the platform, the new Start screen will just be constant reminder for users that Microsoft mucked up. Worse, it will be between them and the real desktop.

There’s a great deal more to say about how you actually use Metro, which leads me to my next point.

Designed for Fingers and Mice

In many ways, the current phone and tablet platforms use touch as a replacement for a mouse. Touch-and-hold menus open up the equivalent of right-click context menus on iOS and Android. Instead of creating touch equivalents for mouse movements, Windows 8 uses gestures for everything. Of course, if you have a keyboard and mouse connected, the OS works perfectly with them too. Hell, it even supports pen computing, if that’s your bag. Each input method follows its own set of rules, which was confusing at first, but quickly made sense to me.

The touch gestures are clearly the focus though, and it seems like Microsoft has designed Windows 8’s touch interface to be more than just a finger-driven mouse. Gestures are intuitive, simple to execute, and speedy. Want to resize a tile on the Start screen? Swipe down from the top of the tile and a context-sensitive menu appears at the bottom of the screen that lets you resize, uninstall, or unpin the app. Want to move it? Just drag. Want to switch between open apps? It’s as easy as swiping from the left side of the screen. Swipe from the top or bottom to access the context-sensitive menu for your current app. And when you need to access more advanced functionality that transcends a particular app? You swipe from the right side of the screen to access Charms.

Charms have an unfortunate name, but they’re important to the new UI. They’re designed to make advanced tasks available to users in the touch environment. There are five Charms: Search, Share, Start, Devices, and Settings. Each provides context-aware functionality to the user from within an app. For example, you can’t drag and drop files in Metro-style apps. Sure, drag and drop always sucks with touch, but the larger problem is Windows 8’s Metro UI lacks windows to drag files from or drop them into. Rather than gin up some complex gesture to replace drag and drop, Microsoft added new super-APIs (they call them Contracts) and exposes them using Charms.

Take the Share Charm for instance. When you tap the Charm from the Pictures app, it opens a dialog on the right side of the screen that lists all the apps you have installed that allow you to share photos.This works the other way too, if you want to add a picture to an email, click “Attach” and the file browser will open up. From there you can add pictures from your PC or any of the photo-sharing services you’ve connected to your PC. The other Charms add support for printers and projectors as well as Search and a shortcut that will return you to the Start screen.

And, if you don’t like touch, or don’t have a PC that supports touch, you can always just use a mouse and keyboard, whether you’re in the new Start screen or the traditional Desktop.

Windows Will Be Integrated with the Entire Cloud

Windows 8 will be tightly integrated with Windows Live, Microsoft’s cloud services. Your preferences, profile, and installed Metro applications will sync across all your Windows 8-powered devices seamlessly. Let me say that again. Your Windows preferences will sync across all of your devices. Seamlessly. When you change your lock screen wallpaper on one device, that will propagate out to all of your other machines in a matter of moments. Apps will also be able to save their data to SkyDrive, Microsoft’s cloud-based storage service.

In addition to Microsoft’s own services, Windows Live also aggregates the connections for your non-MIcrosoft services as well. Once you connect Windows Live to Facebook, Flickr, Picasa, Gmail, and others, those services will be available on any Windows 8 device that you’re logged into with your Windows Live account. This is a good thing--whether Microsoft’s photosharing service is good or not isn’t relevant, people with massive photo libraries on a competitor’s service are unlikely to switch. Windows Live essentially acts as a proxy for other services.

Windows 8 Loves Ambient Data

Whether you’re talking about the Lock screen or the Start screen, there’s ambient data everywhere in Windows 8. I’ve already talked about the constantly-updating Live Tiles on the Start screen, but the Lock screen is worth a look as well.

By default, the Lock screen includes the time and date, battery status, and wireless status. But you can add notification badges for specific Metro apps, as well. Because Windows 8 supports iOS-style push notifications, those badges will live update, even when the PC is in standby. Ambient data on the lock screen is nothing new for phones, but it’s something that hasn’t made the jump to PCs until now.