I was in Harvard Square today at stopped off at the new Flat Patties within the JFK Galleria. It is part of the foor court there and has a very simple menu. It specialized in burgers. I had a cheeseburger ($3.20) and it was delicious. The roll was fresh, soft and very tasty. The burger is flat, so not very thick, but it was flavorful. And for the price, it is well worth it. I did not get the french fries but they looked pretty good.
For anyone looking for a cheap, good burger in the Square, check it out.