Built in mediawiki search is ... well it's already ok, especially if you practice a bit. And you are not constrained to plain search, there are a number of diff

Built in mediawiki search is ... well it's already ok, especially if you practice a bit. And you are not constrained to plain search, there are a number of different systems you can use to organize and browse through your data. Of course there are also a number of semi-external search engines you can add on if you want that can improve results for plain search. Finally, mediawiki tends to be a fairly rich/high quality data source for general purpose search engines to ingest. If you have a reasonably sized intranet that also happens to have a mediawiki wiki on it, you might end up getting better results for everything, not just the wiki.