It runs all weekend long, so you still have you chance to hit it, if you haven't been before. I had the spinach pie (flaky, with a good thick filling) and a nice spicy greek sausage. R had the lamb shank, which was nice and tender, and the roast potatoes which were vinegary (I wasn't a fan). For dessert we had loukoumathes, crispy fried dough balls soaked in honey and covered in walnuts. This is Bri's favorite dessert (and probably the reason we go to so many Greek festivals); I've seen him pack away 28 of these little golden balls of goodness. He had 12 (he is on a diet, you know :)). Our friends Ivan and Betty were also there; he had the lamb also and she had the beef kabob, which they stated was good.
So, out of the 4 festivals we've been to this summer (Cambridge, Somerville, Arlington, Watertown) I can say that all were fun, with decent food, but Watertown's roast lamb sticks out in my mind, and none have anything as good as the octopus salad at Farm Grill in Newton.