A quick, rather inconsequential note: I have migrated Avarthrel Wiki to PostgreSQL database, because I use PostgreSQL for just about everything else already. It was a pretty interesting exercise, and installing MediaWiki on PostgreSQL was certainly far less painful than it was before, when PostgreSQL support was still new. However, the transition still wasn't without friction: had to reupload images (only got back the image pages), the logs and statistics were pretty blank and had to be rerolled (and I don't know how I can get the logs back for real), user accounts with no edits are gone, the deleted revisions are gone for good (well, I only deleted complete junk anyway)... But the bright side is, at least I don't need to run MySQL on my computer right now.
At the same time, I took a look at the Semantic MediaWiki extension. This would make editing the wiki site much more interesting because it'd allow more thorough categorisation of the articles, factoids and like. Unfortunately, it also relies on new database tables, and the PostgreSQL support appears to be "experimental", which is just a nicer word for "doesn't actually at all". It would have been fun if it had actually worked!