(1) It lets you search for a contiguous multiple word expression. Previously, if you searched for <system crash>, it would list every page that had the words <system> and <crash> somewhere on the page, even if they were paragraphs apart and unrelated. With the new search engine, if you do an AND search, it will only report back instances where the words <system crash> are actually adjacent.
(2) It reports back each specific instance of a match on a page (rather than only reporting the page once), previews the line that contains the matched text, and takes you to the nearest anchor to the matched text (rather than just to the top of the page). This should all greatly facilitate your ability to find a specific item.
A few kinks still need to be worked out (as detailed in the notes on the search engine page). But it is far enough along that I wanted to bring it online now. A very grateful thank you to Benjamin Trott, who designed the new search engine.