I just discovered DekiWiki (http://doc.opengarden.org/DekiWiki) and thought I'd share it with others on this list (I don't believe it has been mentioned on here before).
DekiWiki is a fork of MediaWiki (appears to be based on the 1.4.x line). They have provided numerous features that many on this list desire from MediaWiki, including WYSIWYG, granular access permissions, a definite page hierarchy, and per-page attachments. It is worth noting that the target audience and desired usage of DekiWiki is substantially different from MediaWiki's. I would say DekiWiki is more like Confluence or XWiki than MediaWiki. As such, many of the MediaWiki features you have grown to love (including the wiki syntax) are not included. So, evaluate with care.
I'm not trying to incite rage against MediaWiki or actively praise DekiWiki, I'm just trying to spread the word. The MediaWiki developers will acknowledge that MediaWiki serves a targeted audience and getting MediaWiki to play nice in some environments (per-page access permissions, for example) is like pounding a square peg in a round hole. Well, DekiWiki might be your round peg and you might even be able to salvage your MediaWiki knowledge when it comes to hacking DekiWiki.
Cheers,
Gregory Szorc gregory.szorc@gmail.com