I stayed at Melis's apartment with my 70 year old parents.
We loved everything about it. Melis was very responsive to questions before we arrived, and arranged our transfer from the airport. The apartment itself is great - a good size for up to four people and really funky. Melis left us a bottle of wine and some local snacks, which was much appreciated.
The area was perfect - this is the best area in Istanbul to stay! Lots going on, great cafés where both locals and tourists hang out. Very close to public transport.
I would definitely stay at the apartment again. My parents are still raving about it!