It's just like Google huh? Imagine that! 
The search is powered by the Google Custom Search Engine product. We knew we'd never be able to do a search feature that good so we went to the pros! The only down-side is there's a delay between when a new article is posted, and when it will be searchable. Just have to wait for google to reindex us (they do it once a day or more on average).
It indexes/searches all content on the site. Posts, comments, forums etc.
I'm glad to hear people have noticed and are liking the new search. It was one of the bits of the site I was responsible for (not placing it on the page, but selecting it, defining the search parameters, configuring the service).
