oh, and in case anyone was wondering, this is the actual first Lab solution as published :-
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.EditorInput;
using Autodesk.AutoCAD.Runtime;
public class Class1
{
[CommandMethod("HelloWorld")]
public void HelloWorld()
{
Editor ed = Application.DocumentManager.MdiActiveDocument.Editor;
ed.WriteMessage("Hello World");
}
}