Microsoft has been testing a variety of Windows 8.1 builds internally, and some of those software milestones have made their way onto the internet. The latest, build 9385, hasn't been leaked to file sharing sites, but screenshots are starting to emerge that reveal some additions to Windows 8.1. A new lock screen app setting appears to let Windows 8.1 users choose an app to show alarms. Existing apps do not currently support the feature, but it's believed that third-party app developers will be able to create alarms, as well as notifications, for their applications.
Windows 8.1 build 9385 also includes improved developer tools for IE11, with a new interface for accessing debugging and other options. A previously discovered "Kiosk Mode" appears to have been renamed too, referenced as "Assigned access" in the latest builds — a quick way to lock down a user profile to a specific Windows 8-style app. A boot to desktop option and start button are still not present, but Microsoft is understood to be adding both to the final versions of Windows 8.1. A public preview build is still expected to be made available at Microsoft's Build developer conference in late June.
Update: Windows 8.1 build 9385 has leaked to file sharing sites.