After wandering (somewhat) aimlessly through Downtown Toronto, going up into the CN Tower and subwaying it over to Danforth for lunch, Messini is an awesome choice for a very good (very big!) meal. I have a fair amount of experience with Greek food being from NYC, but this place blows everything out of the water as far as I'm concerned.
They have a great lunch menu with your typical assortment of gyros, pitas, souvlaki, etc. I had the pork gyro which was excellent and service with these great Greek-style crinkle cut French fries (and fries in the pita as well!?). The food was fresh, flavorful and served promptly. The lunch special includes a beverage, so for something like $8.00, you have a great meal.
There was a big lunchtime crowd when we went and the place itself is nice and modern and the service was fast and efficient. A little excursion over to Greektown will be worthwhile if you come to Messini.