One more thing to improve is the linking on the wiki. Many times I
get to a wiki page by searching a special topic by inside (wiki search)
or outside search, but could not find it (easily) through the wiki menue
hierarchy.
Absolutely true from my experience.
The wiki search is pretty bad unfortunately...
One proposal might be to put some of the menue structure from the main
page to the side navigation bar of the wiki.
If you want to restructure the main page with the menu on the side you
can just create a new main page and post about it here and everyone can
comment on the new page without always changing the current one...
And I agree that we should add (or move) some categories to the permanent navigation bar.
Cheers, Felix