The beta is an update to the technology preview of the software that was leaked in May and officially released in July, though the most notable changes here are merely a "refined" interface and new program icons. The leak reportedly requires a product key to install, but Technical Preview keys seem to be working just fine.
In addition to its desktop applications, Microsoft is also readying browser-based versions of Word, Excel, PowerPoint, and OneNote. Preview versions of the first three were released back in September. It's unclear if they will also see an update next week, all Microsoft is promising are "some exiting news" at PDC. (Image source: Craving Tech)