I want to evaluate the new sandboxing mechanism in Windows 8/Windows Server 2012. I searched MSDN site for any resources but the documentation is extremely scarce. In comparison with FreeBSD Capsicum documentation, the one provided by Microsoft is just unusable.
How are we supposed to build robust sandboxed apps? Are the sandboxing APIs intended for metro style apps only?
I'm not sure what you mean by "sandboxing APIs". All "metro" (Windows 8 UI Applications) are sandboxed. I'm not aware of any way to sandbox desktop applications in the same way. See here.
Metro apps are pretty tightly sandboxed, and apps submitted to the Windows Store need to declare many types of capabilities that they use — not unlike Google Play's permissions list.
. . .
Windows 8 features a specific SDK for Metro style apps . . .