I've upgraded wiki to rails 2.1.0 , there is a problem with cookies but you can patch rails
gems/actionpack-2.1.0/lib/action_controller/session/cookie_store.rb and change MAX from 4kb to 16kb

here is my git repo new this one :

http://github.com/JakubOboza/instwiki_update/tree/master


i did not upgrded rss/xml's yet :) but i will soon.

sorry for mess