Great location! Nadira's apartment is accurately described. Despite the odd entrance to the building, the apartment itself is beautiful and tastefully furnished. We had a great stay and enjoyed the walks to Topkapi, Sultanahmet, Karakoy, Beyoglu and Eminonu/Sirkeci area. The manager was available to address any issues. Basic conveniences, the pharmacy, grocer, and a small supermarket are readily available and you can have your purchases delivered. The apartment is close to metro station.
The only concerns about the apartment are that there is no elevator, so pack light, and it can get noisy at night given that it's only steps away from Galata tower. Keep in mind that Istanbul is a crowded and dense city, so this is expected in most downtown locations.
On the bright side, those who are new to Istanbul can locate the tower (and the apartment) even across the strait or golden horn.