If Google Flights, despite the fears of many, hasn't come to dominate airfare searches the way it has web searches, it's certainly not for lack of trying or of new features—of which it's just added a few more.
One of the probably most useful: the software will now alert you to flights from other cities that might be cheaper than your original choice. For many travelers, the trip starts with a long drive to a major airport. If you live in Rockford, Illinois, say, and ask Google Flights for a flight from Chicago to Los Angeles it might advise you of a cheaper flight from Milwaukee, not much further away from you.
Like other flight searches, it can also let you know of savings to be had by shifting your dates by a day or two. It also now has the ability to search by alliance or partners, which makes it easier to locate possible award flights, or to judge when to pay cash and when to use miles.