I stayed at Ergul's place for 3 months. The size of the Studio apartment was perfect for me. I liked the modern design. The location was great. Being so close to Taksim Square, Gezi Park and the Metro was perfect. Being situated between Istiklal St and Tarlabasi Blvd was another big plus. So many places to get food, shop, and also grab a Taxi or Bus. If Turkish food isn't your thing just know the apartment is a 1-minute walk to McDonald's, Burger King, KFC, and Papa Johns. However, I highly recommend the Turkish food as it's amazing and very inexpensive.
Very safe area. I found Istanbul, in general, to be very safe and I say that as a New Yorker. I personally didn't have any issues in my 3 months in the city. I look forward to visiting Istanbul and staying here again in the future.