Interesting. I find the switch to 3row textarea from content a little jarring. A further developed version could make use of contentEditable to provide the same editing ability but without the negative side effects of the textarea.
Actually, showing the original wikitext is one of the goals of this user-interface. The goal of this project is to lower the barriers for novice users, and providing a better way for them to learn the wikitext syntax. Hiding the wikitext completely would defeat this purpose.
In the best cases novice users would first edit some sentences, while noticing the wikitext syntax, but only some links and perhaps bold/italics. This is much less scary than a big textarea with lots of code. Then they may experiment with references, images, templates (once these are implemented), so they can slowly learn more. Eventually they can either be advanced users of this editor, or try the editor we have now, which will always be more powerful. The editor I'm proposing *isn't* a total replacement for the current editor, just an addition.
Best regards, Jan Paul