None of us techie types like wysiwyg editors, we all know they generate awful HTML, some of them even use FONT tags still! The problem is clients need to add text to their sites, they need to format it, and they really don't want to learn HTML.
The problems really start when you try to ensure a good seperation of content and design, using carefully constructed CSS rules around semantic HTML and a rigid CSS class vocabulary. For example on our site, surrounding content with a div and blockquote results in the text being padded and surrounded with pretty quote graphics. This is great when the content author knows this, dips into HTML mode in the editor and enters the couple of tags needed.
Of course, you can't expect your clients to do that. What is really needed is an editor tightly integrated into the sites stylesheet, that helps the user markup their content in the right way without even knowing it. It needs to be easily configured by the web designer who defines the markup structures, and it needs to be context sensitive to different areas of a site.
I've tried to do this in the past, we had something similar where I used to work. What I'm imagining is a little more complicated, so it can be used to generate complex sets of data. Definition lists, site specific structures, hCard and hCal microformats. I think FCKEditor is probably a good platform to build this off but I need to have a look around first, check it doesn't already exist!