Maybe i'm completely uninformed but what is the real benefit of .NET.
You can use the Visual Studio .NET IDE (never worked with it, but
Visual Studio 6 is a pain to use).
And it is easier to get alien like looking library wrappers that still
need to be rubyized by hand. I don't see a real advantage here in
contrast to use (and extend) the SWIG tool.

And most libraries are only for windows. The mono project has a complete other
goal then Microsoft when it comes to libraries. Read the announcements carefully
and you will find that they use it to interact other languages more
easy, but they seems not to be interested in realeasing a large and
complete set of libraries. Simply because they don't have to money
that SUN has and can't hire 100 programmers in Bangalore.

So i would recommend to forget about .NET and put our focus directly to the
libraries and the core language implementation. There is enough work
to do.

By the way, if you want to change the threading support you completely break
the language. Can you tell me if .NET supports fibers ?