I have been to Turkey three times. I did get sick once very briefly at Ephesus. One minute I was totally fine, and the next minute I broke out in a cold sweat and started feeling faint and nauseous. Two hours later, I threw up, and everything instantly became normal again, as if nothing had ever happened. I still don't know what that was all about or what caused it. My guess is that I ate something tainted at breakfast at our 5-star hotel in Izmir. I have had similar things happen occasionally in the US, and I honestly think that whatever it was could have happened anywhere. Nobody else in our group got sick.
I basically agree that you should stick to bottled water and generally be reasonably cautious about uncooked food. At the same time, I am not nearly as diligent in Turkey as I am in, say, Egypt. I eat food from street vendors and neighborhood restaurants without hesitation, and I can't say that I am 100% diligent about brushing my teeth with bottled water. In rural areas I tend to be more cautious than in big cities.
I recall hearing a good general rule of thumb: if you can't flush toilet paper down the toilet then the sanitation system is probably not up par and you need to be extra cautious about drinking the water. I have encountered very few of those situations in Turkey.
As for medications, I always pack some Pepto Bismol and Immodium, the same as I would for a trip to Europe.