From developer's perspective it's two modern mainstream languages - F#, C# - that can be used on Windows, Azure, Mac, iOS, Android, WP as a well-defined workflow.
The best IDE - Visual Studio + ReSharper + soon Roslyn. Second best ecosystem of libraries, that is picking up.
There are some missing bits that are coming: docker and containers, dynamic compilation (of static typed code) when building web sites.
It might not be the best choice in individual "disciplines", but it's the best overall.
I've found the best value/growth combination to be Linux, Mono, and F#. If I need a database I'll use something free or open source.
Right now I think folks are making a mistake if they decide to go "all Microsoft" or "no Microsoft". It's much more nuanced than that.