Mediawiki is the engine that powers Wikipedia. While that gives it lots of props, it is writen in php, which has historically had security issues. Over time, I’ve gotten over my php alergy, mostly because WordPress is just too damn good (and what runs this site).
Over the past year I’ve fallen into running 3 media wiki instances… and I’m impressed. So, I made converting mhvlug.org from MoinMoin to Mediawiki as my Linux Fest project yesterday. 2 hours to port our theme, an hour to figure out how to export / import all our content, a couple of hours tracking down how to get short urls to work right, then an hour or two of deleting pages that probably shouldn’t have transfered in the first place, and we’re done!
It’s also amazing how much more you use software you really love. I’m definitely a fan of mediawiki at this point, and being able to use things I learn in one instance on other instances is really handy.