Honestly I don't believe the pictues do this flat the justice it deserves, the view alone is priceless. Memet was a great host, and gave me some good suggestions in Taksim.
Everything you need is within walking distance, transportation, restaurants, bars and nightlife. The location is fairly central and you can quickly get to the ferry, train, bus, or find a taxi. The flat is just off of Taksim square, so it can be loud at night, having said, that Taksim is a busy district and if you want a quiet and get away you probably shouldn't look in taksim.
The only other thing I would note is the flat is on a hill and is a five floor walk up, if thats a deal breaker for you be aware, but also know that elevators aren't common in Taksim.
Beyond that it is an amazing place and I will defenitly try to stay there again the next time im in Istanbul.