The apartement is in a really good neighbourhood right between Beşiktaş and Nişantaşı, the former offering bars and restaurant, the later offering cafes and shops.
Due to the central location you can reach all touristy places fairly quickly by either bus or metro.
The apartement itself is not huge, but it offers all the necessities, including a fully stocked kitchen and a washing machine. Towels were offered by the host. The kitchen and living room are on a souterrain level, but the two bedrooms overlook a courtyard witch is 2 levels above street level, so noody will disturb you while sleeping.
All in all it was a great stay, and we would recommend it for your next trip to Istanbul.