Microsoft makes it a point of not sharing all of interim Builds of next generation product available to all testers, and this is also the case for Windows 8, the successor of Windows 7.

But although there isn’t much information available on Windows vNext, the company is hard at work building the operating system, and also dogfooding it.

Dogfooding is a term synonymous with internal testing, and Microsoft traditionally has its employees running next version of its products, Windows included, even at the very early stages of the development process. Think pre-Alpha and Alpha.

Or in the case of Windows 8, Milestone releases, just as for Windows 7. Third-party reports indicate that Windows 8 has reached Milestone 2, and that it’s on its way to M3.

Windows 8 Development Process Still in the Early Stages - Softpedia