Right, that didn't work out at all. I don't know if it's because I installed Mono 1.2.4, or if it's just busted, but Xcode says the build succeeded, but there is no executable in the build folder, and not error messages. It might be related to fact that the Product has a blank named file in it, but I am sure not tearing into the project templates and all that to figure this out especially when this is nothing more than syntax highlighting for C# in Xcode and for command-line programs at that, no ASP.NET based stuff at all, and no IntelliSense. Ok, back to figuring out MonoDevelop for OS X...*sigh*
Update
A comment on this post says its from Susan, the original developer of the plugin. So I screenshot exactly what I did even in the trivial case in the documentation (which yes I did read - mostly ;-))
Now to build...
And there is nothing to run...