This is very cool, this my friends, is brand new built from the ground-up Operating System, it's a 21st Century Operating System based entirely on concepts from the .NET Framework and it's been published on CodePlex!
It's only a research project, but demonstrates some very powerful properties such as Software Isolated Processes (SIP), because all code in the operating system is in IL, it is effectively sandboxed by the underlying OS runtime, without the need for hardware enforcement. All code can safely run in ring 0 (e.g. Kernel mode) avoiding the need for kernel/user transitions, due to the lightweight nature of SIPs each device, OS component and application can run in its own SIP providing modular reliability guarantees not possible in a monolithic design.
Memory management becomes much easier too, thanks to managed code and the operating system's Garbage Collector.
They've also made some very good design choices that make a lot of sense: processes cannot share memory and cannot modify their own code. They've developed a fast and reliable contract-based messaging mechanism for inter-process communication.
Windows was designed at a time when we didn't have the luxury of managed code, when hardware resources were limited, when web services didn't exist, when computer performance was a fraction of what it is today. The Windows team has done its best to keep pace industry developments, the rise of the internet and the different numerous ways we want to use our computers today, in some areas it has risen to the challenge admirably, in others, it's take a lot of engineering and effort and there's still more to be done (think security).
Thankfully, singularity has had time to reflect on the last 25 years of computer operating systems and incorporates some neat ideas into this brand new (research) operating system.
I'd encourage you to take a look, it's a fascinating concept.
http://research.microsoft.com/os/singularity/
http://www.codeplex.com/singularity
Also, check out the videos!
Singularity: A research OS written in C#, Channel 9 video and blog, Redmond, WA, August 23, 2005.
Singularity Revisited, Channel 9 video and blog, Redmond, WA, December 13, 2005.
Singularity III: Revenge of the SIP, Channel 9 video and blog, Redmond, WA, September 1, 2006.
Singularity IV: Return of the UI, Channel 9 video and blog, Redmond, WA, September 1, 2006.