The location was great, you can walk to a number of good places and you're close to most transportation systems. The street is on a flat surface, which is kinda rare in Istanbul, so that was a bonus. The receptionist is very polite and kind (from the moment he stepped in when we had a disastrous arrival as the owner gave us the wrong location to the moment we left). The elevator - albeit small - was also a good thing (oldie but goodie). The apartment is very basic and smaller than it looks on the pictures, but as all the building units are furnished the same way, we might have been confused. The first one we got smelled really bad, but luckily, we switched to another apartment after a few days, and the problem was solved.
Our stay in Turkey was rather long (over a month) so we needed something good and practical, hence our disappointment when, contrary to what was advertised, we found no washer in the unit, knowing that this was one of our search criteria, just like AC and Wifi. There was a free laundry service, though, but it was quite a hassle so we only used it once.
Now, to the tips part: if you want to cook, bring your own stuff: the kitchen has the bare minimum (i.e a few cooking utensils but not even a drop of oil or a pinch of salt or pepper). If you need to iron your clothes often, bring your own travel iron, getting one isn't easy. In our case, we only borrowed it once and as everyone was using that one iron, we had to wait to use it and then we had to give it back fast. Overall, the apartment is okay for 2 people, but I wouldn't recommend it for more. The location is very good, especially if it's your first visit as you can get to see most of the city highlights without having to waste any time in transportation (this was my 5th visit but the location was still convenient). Also, if you're not a vegetarian and you happen to stay there, you should definitely eat some Tantuni at Suat Usta Mersin Tantuni. It's tasty and their prices are very reasonable.