This entire post by Microsoft’s Steven Sinofsky could just be shortened to: “We’ve copied Time Machine for Windows 8. I don’t know why we’re just now getting around to this, being the world’s most popular operating system and all, but here it is.”
One big caveat though (emphasis mine):
File History is a backup application that continuously protects your personal files stored in Libraries, Desktop, Favorites, and Contacts folders. It periodically (by default every hour) scans the file system for changes and copies changed files to another location. Every time any of your personal files has changed, its copy will be stored on a dedicated, external storage device selected by you. Over time, File History builds a complete history of changes made to any personal file.
Compare to Time Machine:
Time Machine automatically backs up your entire Mac, including system files, applications, accounts, preferences, music, photos, movies, and documents.
Time Machine backs up everything on your Mac, including applications, email accounts, settings, and all your files. Windows 8′s File History will only grab items in your Libraries, Desktop, Favorites, and Contacts folders. There are quite a few important items stored outside these folders in Windows (Outlook files, application data stored in the user folder, web browser data, etc), so unless there’s a workaround to back those up as well, we’ll have to continue using 3rd-party backup software for many of our Windows users.
Which is a little sad, becase there’s no reason Windows users should have to pay 3rd parties for basic, reliable file backup.