Windows 8 (build 7850) Milestone 1 is basically Windows 7 with some new additions and features that Microsoft has been working under the hood. But they are kinda locked up, and not visible in any menu. They can be only dug up deep in Windows 8 files and registry.
Windows 8 Tweaker is a free utility that allows users to unlock hidden features/programs in Windows 8 (build 7850). Hidden Windows 8 features like enabling modern task manager, enable webcam app, Windows 8 PDF reader, Windows 8 Ribbon UI etc.