Hi!
I've read that usability is important for MediaWiki. Why don't integrate
wikitext syntax highlighting then? That will greatly improve editing of
the pages. There is Extension:WikEd which has most of the work
implemented already.
http://www.mediawiki.org/wiki/File:WikEd_screenshot.png
I know that it should be possible to install the extension separately.
But I remember that important extensions are sometimes integrated into
MediaWiki.
There's also FCKeditor, but it cannot perform diffs, and visual editing
is not always desirable (non-technical users like it, but I personally
prefer to edit wikitext).
It just comes to me everytime I edit source PHP with hightlighting, then
editing wikitext without highlighting :-(
Dmitriy