Finally made it for lunch after reading (and re-reading) reviews during my last couple trips to Pittsburgh. I can say it lives up to the hype. The food is very good, authentic and the service is very pleasant. My only piece of feedback is that their menu system is a bit confusing and it gets very busy during the lunch exacerbating the situation.
I ordered a mixed lamb & chicken pita sandwich which comes with a pre-dressed simple salad. I added a few cold items on the salad for an extra charge. I went with the baba, eggplant and white beans. I told them it was my "highly anticipated first visit" and they gave me smaller samples of 3 other sides. Everything was really good I thought the pita itself (and the spicy sauce they put on it) as well as the white beans were the highlights. Service was quick but if you're in a rush pass on the pita/wraps as the rice/salad platters move much faster.
As many other mention it's cash only so grab cash at the ATMs on the way down. (To find the location enter the Steel building on street level and go behind the escalators up to the next level to find another set of escalators down. Once on the next level down go around the escalators through the doors. Istanbul Grille is at the end of the hall pass the other restaurants.)