I watched the video and the software looks very impressive for what it is. I wouldn't ever use it but for someone who just wants to create a simple static site it seems somewhat useful.
Watch the video. The main take away point is that the semantics are controllable by the user. You could write really sloppy HTML or very semantic HTML based on your understanding of HTML.
Edit: I've been going through the videos and this actually looks very impressive. It isn't really your standard WYSIWYG editor. I guess you could use it like that but it is more GUI for CSS and HTML. I would say it is a new class of product from what most people would refer to as a WYSIWYG editor.
I wonder if there is any integration with dynamic server side scripting.