Spent 4 nights (New Year Eve included). Our stay was surprisingly good. The apartment was very cozy and provided us with the perfect base point to explore old Constantinople. We never rented a cab or took any public transport. Each day we walked by foot to all sites we marked for visiting. To cut it short, here's a summary:
Pros:
+ the location is perfect (10 min. from waterfront, 15-20 minutes from historic center, yet far away from large crowds)
+ noticeably fresh sea air in the morning
+ the place was very comfortable
+ clean bathroom with unlimited hot water
+ good cafes and restaurants within 100m
+ host was very responsive and helped with the parking
Cons:
- on 3-4 occassions some conjestion occurred on the street in front of the apartment leading to angry car horns noise. Street noise was not really an issue though.
- water pressure dropped for ~1h, but I assume this was not specific to the building.
Conclusion: will definitely book again if I visit Istanbul in the future!