The apartment is great - large, clean and you would have everything you need. I needed a desk to work on, so I contacted the owner and they delivered a new desk and an office chair the next day. They were very accommodative and strived to make our stay perfect, and they replied to all the questions promptly.
Location is perfect, there are nice restaurants and cafes nearby, Istiklal street, Taksim square, Galataport with the sea promenade. Also the street is not noisy, so we could sleep with open windows. I would definitely stay there again if I ever in Istanbul.