We enjoyed our stay at this apartment and would totally recommend this place for anyone wanting to stay in the old part of Istanbul!
It's perfect for 2 people, warm, clean (it's actually serviced daily), hot water works perfectly, internet was ok but cut out sometimes but always reconnected after a few minutes or so. One evening we completely lost power but it affected the whole street so it wasn't a problem at all of the apartment itself.
It's on a side street from a small "mini-main" road so its nice and quiet during the night. It's within walking distance from most of the main sights, and only 10 mins walk from one of the main tram stations (but take note, on the way back up to the tram station, its a relatively steep walk up cobblestoned roads. It was absolutely no problem for us, but if you're not inclined to walking up steep roads every morning, it could be a downside). Another benefit is that right next to the closest tram station is the Grand Bazaar so the location is definitely a benefit. Lots of nearby restaurants and little grocery shops.
Would recommend!