One of the new features in Windows 8 that I'm particularly intrigued by, mostly because I've been asking for this for years, is the ability to log on to the PC with a Windows Live ID instead of a more traditional local user account. Today, on the Building Windows 8 Blog, Microsoft group program manager Katie Frigon tackles this new feature and provides some interesting context.

"In Windows 8, we have set out to ensure that each PC user has a truly personal experience that seamlessly bridges their online and offline tasks, is simpler to set up and use, and persists across their set of Windows 8 PCs," she writes in the blog post." To do this, we've introduced the ability to log in to Windows (optionally) with a Windows Live ID that works across devices, apps, and services, allowing you a uniquely personal experience with Windows."

So what are the differences between logging on with a Windows Live ID and just using a local user account? With a Windows Live ID you get the following unique capabilities:

Windows settings. The "most commonly used Windows settings" are associated with your Windows Live ID and persist to each PC on which you logon with that ID.

Metro-style apps. The settings and last-used-state for each Metro-style app (but not "classic" desktop apps) is persisted to each PC you associate with your Live ID. "Let's say you are reading the news in a reader app on your tablet," Frigon writes. "If you add specific feeds you want to continue to follow, those feeds could automatically be available in the same reader app on any of your other Windows 8 PCs. We will also enable developers to build Metro style apps that tell Windows their state, so you can pick up where you left off as you move between PCs."

App and web site credentials. For each Metro-style app or web site that requires a logon, that authentication information will be stored with your Windows Live ID, and auto-propagated to any PC which you logon to with that ID.

Auto logon for Windows Live-based sites. You will automatically logon to any Metro-style apps and web sites and services that use your Windows Live ID for authentication.

Using a Windows Live ID style logon is optional and is in fact not available during Setup if your PC isn't connected to the Internet. But if you are connected, you can opt to logon to existing Windows Live ID or create a new one as part of Setup. (Or later, via Control Panel.)

You can also control what's synced by turning off all syncing or by turning off syncing per the type of setting. Available settings groups include Personalize, Themes, Ease of access, Language preferences, Apps, Web browser, Other stuff, and Some passwords.

There's a lot more information about this feature in the blog post, including how Microsoft stores this data and what the privacy and security implications are. So be sure to read the original post as well.