Microsoft has done an incredible job of keeping the .NET Framework powerful and stable. It is well designed and keeps getting more robust with each release. It isn't the most popular technology in this space, but I think a good case can be made to use .NET in many new projects.
As we started on Windows Phone we use C# and .NET for most of our apps and sites. Being a small team of 2, using .NET enables us to work on each part of the service without having to switch to different languages.