Update: It turns out the screenshot is actually
fake. Perhaps a similar feature will surface eventually, but right now it does not exist.
According to WinBeta.org, the latest internal Windows 8 build as of 21st June is 8030.0.110620-1742.
WinBeta went on to share a screenshot, which appears to show more of the Immersive UI, that Microsoft unveiled at the Computex and D9 conferences.
Notice in the bottom right corner, evidence can be found of a newer Notification System, possibly designed to work with the new interface so users don't have to continually revert to the tradtional Windows desktop, in order to check system notifications.