We had a pretty lengthy discussion about this before the summer, and the
consensus seemed to be that a fulltext-based approach looked most
viable. I actually wrote an extension that does that, and promised to
release it soon; that was quite a few months ago, and I never got around
to it. I'll release it properly when I have time, which will hopefully
be before Christmas :D
The code needs some tweaking and refactoring, though. It's pretty
tightly integrated with the article text search (both functions in one
form) and has all kinds of weird features, because the guy who paid me
to write it wanted them. It also doesn't support three-letter word
searching (which core does these days, using a prefix hack), which is
pretty bad since categories with short titles (or stopword titles) won't
be found either.
Roan Kattouw (Catrope)