The national carrier of Turkey is my favorite major carrier. They knock Lufthansa out of my top spot this year. Entschuldigung Lufthansa, but your cost cutting and competing with the low cost carriers has hurt, not improved, your business.
Turkish has a large route network, all focused through Istanbul. Be sure to check where you are flying to as Istanbul has two airports. Ataturk(IST) is the hub. It is large and a bit dated. Sabiha Gokcen(SAW) is the smaller low cost carrier airport though some low cost flights go through IST and some Turkish flights go through SAW. I would recommend not booking flights through separate airports as they on opposite sides of this massive city and could take you over three hours to get between them. Pay the extra money to fly through one or the other, or better yet switch airports but spend a few amazing days making your way slowly across the impressiveness that is Istanbul.
The duty free area in Ataturk is as crowded as a Manhatten sidewalk and the queues for everything are ridiculous. But it is still leagues better than an American airport and the benefits outweigh these little gripes. There are pubs with Efes, one of the best beers ever made. It is a Turkish beer so enjoy yourself everywhere you go in the country. It is also possible to easily get to the tourist areas during a long layover. Take a taxi or a metro-tram combo to Sultanahmet. It will take you thirty minutes to an hour. Do know that you have to pay a visa fee to leave the airport. Be sure to go to the visa desk before getting in the immigration queue. The city is one of the most amazing in the world. If you don’t want to go far the aquarium is just behind the airport, so a short taxi ride and you have hours to spend at a fantastic and modern aquarium. It backs to a promenade on the sea with many restaurants and a great view of the flights landing overhead.
Turkish short haul flights are nothing special(the same as any short haul flight around the world). Normal legroom, seat space, et cetera, et cetera. The food and service is better than average and you get Turkish Delight(A gelatin fruit candy).
Long haul flights are outstanding. Service is wonderful, food is delicious, cockpit and cabin crew fantastic. The planes are clean and modern. In-flight entertainment is varied and comprehensive. I have always been on-time and never lost any luggage(unlike Etihad which lost both my checked bags for a week BOTH ways).
There is a reason Turkish Airlines keeps winning Airline of the Year. They deserve it.