Mono sounds like a great project and the community is large. There are a couple of projects i love:
Beagle http://www.gnome.org/projects/beagle/

and

Mono Develop http://www.monodevelop.com/Main_Page

This one instead of using the regular System.Windows.* use the GTK arch to create windows and base its skin to system theme (compatible with gtk arch).

I think will be nice to have a new Window abstraction to merge both Windows and GTK Forms architecture to write completely switchable programs.
But for now, great work Monoers!