HTMLbox looks pretty nice, but I think drupal would do better if wysiwyg was a priority for core, rather than a luxury added via plugins. A CMS should provide appropriate sets of tools to edit content for users of all levels, and at some point this means providing an wysiwyg for markup. Wordpress has pretty much nailed it, UI-wise, for their backend. Sure, wyiswyg's are more of an albatross than anything else for those of us who can do markup, but I don't think that's drupal's target end-user market. We'd probably be just as happy writing SQL queries by hand to insert new nodes -- but our end users (who may or may not be technically competent) need as much hand-holding as they can get. Now, wordpress arguably has an easier time because they have a simpler and largely static set of input filters but a robust editor api would take care of that.

Wordpress's suitability for inexperienced users means that I will almost always prefer building a site on it when possible. The most common complaint I hear about drupal is "It's too complicated", and I think a lot of this has to do with the administrative UI. When I get a chance (working on some other side projects right now), this is something I'd love to help contribute to. Wysiwyg in core would mean more drupal users, which would mean more drupal developers, which would mean a better drupal.

I've only checked the only demo for this editor but I don't like what I'm seeing. The editor allows the user to change the font-style, -size, -color, and -background but doesn't have selectors for block elements (h1, h2, h3, p, address, ...) or css classes.

I don't want my clients to change font-size, -style, etc as they like it. I provide them with suitable css classes. For this, WYMeditor seems to be still the best (http://drupal.org/project/wymeditor).

Check out the demo: http://demo.wymeditor.org/0.5-a1/examples/08-custom-panel.html