I think users most of the time want to search on article titles only.
That should be the default behavior of the little search boxes on
every page (maybe changeable on user preferences page?).
Then there should be an advanced search page where you can search on
article body, with regular expression and all the fixings. Authors
will use this.
If you do a regular article title search, the page with returned
results should say: "You can also do a [[full text search]] of all
articles."
Alternatively, search could remain full text as it is now, but return
the pages with the search term in their title above, and separated
from, the ones with the search term in their body.
Cheers,
Axel