Just back from our whirlwind 2-1/2 week trip around Greece. It was fabulous and I admit I was shocked at how good the food was. I'm going to post some miscellaneous thoughts, in no particular order.
First - I was travelling with 3 friends who would eat no unkosher meat. So I was worried that this would limit my dining experience. Au contraire, as it turned out. We ended up eating most meals as shared mezedes - which I think is where Greek cuisine shines. What those people can do with an eggplant! Anyway, we ate some stunningly delicious versions of standard dishes like taramasalata, eggplant salad, gigantes (giant beans), tzatziki, etc., etc., etc. It was actually a wonderful way of sampling a bazillion different dishes - without the agonizing commitment of having to choose a single main dish. If I felt meat-deprived, I just ordered a meat thing. But mostly I was extremely happy.
Fish is horrifyingly expensive. I am not exaggerating. We went out for one fish dinner in Piraeus at Dourambeis which was really really good, but unconscionably pricey. I mean honestly - ONE SINGLE SEA BASS (ok, it fed 4 of us, but not lavishly) was over $100 (U.S.). ONE FISH!!! It was a delicious fish, very well prepared (grilled) but good grief. Their house salad was unbelievably good as were their merides (tiny fried whitings). It was a nice meal but outrageously overpriced, even given the price of fish at the market.
On the other hand, we had our single most wonderful fish meal in a tiny little village on the island of Sifnos. The village is called Chernissos (or Hernissos, depending) and the restaurant is called Ammodia (or Hammodia, depending). You go into the restaurant and pick the fish out of a big cooler - you pay by weight. Everything was caught right off the beach and absolutely killer fresh and delicious. Not expensive, considering. I think we paid about $20-ish per person and had wine and lots of mezedes and salads.
In Athens, I can recommend 2 tavernas that serve good food at reasonable prices: Byzantino (also known as Vizantino) and Psara Taverna, both in the Plaka. I'm sure there are lots more, but we ate at some others that were not quite as good.
If it's on the menu - try "dakos" (also sometimes known as "takos"). It's a layered salad with a sort of rusk bread on the bottom and usually tomatoes and feta on top. Occasionally it will also have olives and other stuff - really wonderful with ouzo!
I'm sorry but I found the food on Santorini overpriced and underwhelming. Maybe the result of too many tourists, but there were no great Chowfinds there.
Had a very good lunch in the town of Apiranthos on the island of Naxos - at O Platanos taverna on the main street (there's only one). I can't remember what we ate (my notes are incomplete) but I remember the food was good.
Always order the house wine. It's often as good or better than what you'll order in a bottle - especially if you're not an expert on Greek wines (which we were not). If the wine is awful (which occasionally it was) just don't drink it and order something else. But the house wine served in a jug is usually so cheap that it's worth the risk.
The yogurt is indescribably good. So I won't even try to describe it. Let's just say that right now I have a container of yogurt draining through a coffee filter in my refrigerator but it will be but a pale imitation of the Greek stuff.
Visit the central market in Athens if you have the time. It's fantastic. I came home with a suitcase full of (possibly) contraband food - olives, sundried tomatoes, oregano, pistachios, thyme honey, capers - I can't remember what else. Other people come home with worry beads and jewellery - I buy capers. To each his/her own.
Anyway - that's it. If I think of anything else to report, I'll post. It was a delicious trip.