My favorite feature of Google Flights is that you do not need to know where you want to go.
With Google Flights you can enter your point a, and leave the destination blank and let Google do all the meticulous searching for you.
From: Paris, France
What you end up with is a highly interactive map of all the cities in Europe that you could possibly travel to. I cannot explain how useful this is. It is so easy to see the different prices for each trip, and its very easy to book last minute deals. Google redirects you directly to the airline checkout page when you are ready.
Its a lot of fun playing with this website and seeing what ridiculous deals you can find. I booked a one way ticket from Nantes, France to Rome, Italy for $40, 2 days before the flight departed.
Even if you are set on going to one city in particular, I would still recommend Google Flights to you because of the ease of use and aesthetics of the website.
I used Google Flights my entire trip and will continue to solely use it.