So… I’ve got two options here, neither of them totally satisfactory.
1) Use the built-in WordPress search function. It’s pretty basic, though you can install plugins to make it search pages as well as posts, and nicely highlight search terms on the results page. Pro: it only searches post/page content, and title (this annoyed me before). Which in fact is a bit of a con, because now I may want to search the comments. Other con: the search results are displayed in chronological order (timestamp for posts, creation date for pages). No clever algorithms to determine usefulness, even if it’s only giving a higher ranking to search terms in titles.
Other huge con: it won’t search the photo galleries. That runs off a completely different database, and while Gallery does have a search plugin, I think it’d look silly to use two different forms, each searching half my site. Not to mention, I don’t even know where I’d place them.
So it looks like we’re going with (2), a Google-powered search. The same as what I’ve got now? Not quite. I’ve registered a custom search engine which should do pretty well. It’s nothing fancy, but it will allow me to style the results page to a degree. There’ll be ads, but I can live with that. And it’ll make my job a lot easier, since I don’t have to worry about formatting the output of two different search engines.