Big loss for Microsoft.
Its possible to sway the windows developer community to branch out and hopefully more people in the community will take initiative to sway others to do so.
http://www.zdnet.com/blog/microsoft/microsoft-reorg-scott-gu...
IMO MS is too much driven by profits and control to realize expanding the .NET OSS community will be a NET win for their .NET platform and surrounding tooling / aspirations.