Currently we use a MediaWiki installation for writing documentation, but several of us find the markup format horribly arbitrary and awkward, with a mixture of Wiki tags and XML in the text, and the lack of any quick formatting buttons for things like ordered or unordered lists, different heading levels, quick embedding of images, tables, code samples, etc. Sites like LiveJournal provide most or all of this while still generating backwards-compatible markup so it's not like there's a technological impediment here.

There are other niceties that we'd like to see, such as being able to pick a category from a list (ala Wordpress) or maybe being able to apply syntax highlighting to code samples, etc.

Do Wikis exist that provide a decent range of these features to make life easier on the editor? Something with the features and presentation of WordPress but the page organisation of a Wiki would be perfect.

(WikiMatrix returns several candidates, but among them is MediaWiki, which quite clearly is not a WYSIWYG interface except in the most tenuous fashion. I'd rather not dig through each one if it's plain that WikiMatrix is not being entirely stringent about its criteria.)