The issue is that, even if power users don't use the new interface they still need to be able to use the old one to edit the same articles. If the wikitext created by the visual editor is unnecessarily complicated and unreadable (like the html produced by ms frontpage, for instance) then there is problem. Similarly, the visual editor needs to be able to parse even quite strangely written wikitext.
^^ This, 100 times over :)
Writing a visual editor is painfully hard. I've just finished one for a current project after we evaluated what felt like a billion pre-existing alternatives. Without fail they all suffered in that their output left a * lot* to be desired.
The key thing to remember is that the output should be indistinguishable from what a power editor would have written.
And cover all the edge cases (because with millions of articles we have lots of those).
However; this looks an interesting start. I like the simplicity.
Tom