Jeff gets offended when this comes up, but it really isn't very good. Most "advanced" users just use "
site:stackoverflow.com <search terms>" to find things, as it is infinitely better.
HOWEVER, I believe there are some improvements being planned that would make the site search more relevant. In particular, things like being able to add
-userid:XXX to search for posts by a particular user and so on. For more on that, check out this questionthis question, which currently has "status-planned"