Stepping towards Hipmunk-style relevance and control, Google Flight Search has rolled out some new features.
Tips
Google now provides a "tip" to searchers looking for the best deal - a convenient way to see how to save money right there in the search interface.
From Google's Fred Brewin, Product Manager:

If you're a budget-conscious traveler with some flexibility in your schedule, a new feature called tips may be able to help you save money.We will show you alternative flight options, so you'll know if there's a less expensive flight a day earlier or later than the date you'd originally planned to travel, or a nearby airport that offers a non-stop to your destination. We'll even tell you if there are inexpensive upgrades to business class on your target travel dates.
Best flight
Similar to Hipmunk's "Agony" metric, Google now sets apart the flights that are most popular with other searchers on a particular route.
Mr. Brewin:

Another new feature called best flights should help you save time by calling out flights that are most likely the best trade off between price and convenience.You’ll see our suggestions -- the flights that most people choose -- highlighted at the top of the list. Of course, it’s still possible to see flights sorted in all the ways previously available -- price, airline, number of stops, duration, and more.
Read the brief blog here, and access Flight Search here.