Positives:

- Great value
- Fantastic central location
- Mehmet was a very friendly and helpful host, both before our stay and during check in
- The airbnb listing is an accurate description of what you get

Negatives:

- Lots of steps (not a problem for us but could be for others)
- Very warm at night (obviously Istanbul is very warm during the summer - if you suffer with the heat, you need somewhere with aircon!)
- Flat and furniture is a little dated

Conclusion: Not a luxury option but great value, location and host mean I wouldn't hesitate to recommend to others!

(my review would be 4.5 star if that was an option)