I still create a lot of plain text documents and a lot of heavily-tagged word-processed documents. But when I want a simple structured document, I just use XHTML. It is NOT fun to write in a plain text editor, so I have searched, on an off, for an editor that will produce good HTML with less typing effort. My latest find is CKEditor (used to be fckeditor). It, likewise, is a script, in this case JavaScript, so it runs in a browser window. It is not my perfect answer, but I like its interface and the documents it produces are fairly well-formatted.

With HTML so ubiquitous, I'm not sure why I would plow around for yet another XML-type language to use for documents. However, ease of typing will always be an issue for me, as I have never been that great at using a keyboard.