Advanced search often serves as an anti-pattern, a lesson in what not to do.
Only a few users actually use advanced search. Perhaps that's because most folks don't speak Boolean.
That said, it may be worth offering advanced features that are useful to a small yet important subset of users.
In any case, with a bit of ingenuity, most "advanced" capabilities can be subtly woven into the main search experience.
Advancing Advanced Search is a nice introductory article by Stephen Turbek.