I do some draping, but generally use a sloper or base pattern to begin with.  Draping is my favorite method for skirts.  I have thought about CAD software, but I think it would be like my graphing calculator (which I don't use) in that I enjoy working with actual paper/muslin and pencil. But I can see how software lets you try out many ideas quickly before you commit to printing a pattern to actually try in fabric.  !CTP