I've been to many Greek restaurants before and have learned to expect the following: lots of blue and white paint; lots of plants; loud music. I expect large-ish portions, and to be charged for extra tzatziki or hummous, or extra pita. It's just what I've learned. Service-wise, ranges from super attentive to mostly indifferent.
We went to Santorini on Sept 20 for my brother's birthday. There were 7 of us in the party. It was fairly early, about 6:30 - the restaurant was pretty empty for a Sunday night. Not sure if that's because it's just a slow night or slow season in general. Our waitress was very attentive - turning down the music in our section, closing the blinds while the sun was glaring in our faces... she even set aside the beer specials for our table because they were running out of the special, and knew that we really liked it. She took hints and filled water without interrupting the conversations we were having... was inscenced on our behalf with the kitchen staff when two of our meals didn't come with tzatziki sauce... separated our bills for us without making a fuss (and let us know that she might not have done it properly)... and at the end, when we paid, informed us that we tipped too much! (For us, she HAD messed up the bill a little bit - charged one couple in our party for some of the drinks I had - so to even it out we had them under-tip while we over-tipped, so she got an even tip overall.)
The food was decent. We had a few different souvlakis - beef and chicken and lamb, spanakopita entree and moussaka entree. The souvlakis & spanakopita entrees tasted great, served with large portions of rice, side of potato and greek salad. The moussaka was somewhat lacking, but might have been a matter of opinion at the time.
Almost everyone went home with leftovers. In my mind if you are paying $16 for an entree and you get two meals out of the deal, that's pretty good value overall.