Zehra's place is a real gem. She really went above and beyond. My S/O and I stayed there for 10 days and were extremely pleased with it. tl;dr at the bottom because I'm wordy.
The location is phenomenal. You're within walking distance of a huge number of tourist destinations. The inside of the place looks fantastic, if not better in-person than the pictures, which is always a welcome breath of fresh air. The area overall was very safe at all hours, so if that's ever a concern for you when traveling, worry not. The place itself is also really easy to find, so no worrying about trying to navigate some labyrinth of side-streets for some hidden alcove either.
If you keep going up the stairs of the building, there's a roof deck with a nice view of the city; and because I know there's going to be another person like me who tries this, yes you can pinpoint it from the Galata Tower. (Use the old building across the main street with the several domes on it as a reference point. That building is also a good reference landmark for when you're walking back to the place at the end of the day. This will immediately make sense when you see it since it sticks out from the buildings around it.)
There's a fantastic restaurant practically right across the street within eyeshot; barely 20 or 30 meters from the building entrance, can't miss it. About a 3 minute walk away is a European-style café called Books and Coffee - for the coffee-fiend in your life who wants a cappuccino. (Or whatever other varietal drink you might want that requires a barista station.) They speak Russian and English very well there, which made orders really easy if you don't know any Turkish. (They also taught me a couple of phrases in Turkish, which was most helpful.) The coffee shop is also right next to the cable-car for about 5.50 lira that can take you up the hill to the Galata Tower, other touristy areas, and that long shopping street with the tram running through the middle of it that I can never remember the name of. It's great. You can also walk up the hill instead of taking the cable-car depending on your mood, as it'll only take you maybe 10 minutes tops.
Random niche side note: If you're from the States and are into tools (or are a fan of AvE on YouTube), there was a shop nearby that had the Bosch mini-chainsaw. The cool tiny green one that's not good for much other than the novelty. Someone out there will appreciate knowing that. (Don't worry about it if you have no idea what I'm referring to, ha.)
tl;dr - The place looks fantastic. Phenomenal location. Safe area. Would definitely rent out again next time I'm back in Istanbul. (Assuming it hasn't been rented already.)