Guys, I just got back after a 5 day trip to Istanbul. Ramadan had absolutely no effect whatsoever.
I wanted to visit Kale for breakfast (Anthony Bourtain's stop) but it ended up being a bit far from where I was staying and a bit inconvenient as public transportation doesn't get you there. I didn't wanna cough up 50 odd bucks on taxis to experience Turkish breakfast at a decent restaurant.
Istanbul is mighty amazing for those that are interested to visit. It's the most beautiful city I've been to.