My 6 family members and I stayed in a 2-bed, 2-bath unit with Noa Luxury Apts. for 10 days and truly enjoyed it. The apartment was modern, spacious, clean, and had all the amenities we needed. Most of the staff at the apartment complex don't speak much English, but they are very friendly and helpful (*hint* Google Translate works wonders). Noa also has a very modern gym with showers and a sauna that are all free to use for guests staying at the complex, and they even offer massages (not free).
The location is fantastic. 2 minute walk from the Galata tower and a 5 minute walk from the nearest tram station. There is also a multitude of restaurants and shops just a short walk away. Finally because the apartment building is in a narrow side street, it is very quiet despite its proximity to the hubbub of the Galata tower plaza.
While there are cheaper options available nearby, overall it's a great place to stay if you're willing to pay for the modern design and amenities. My family and I will definitely consider staying here again if we revisit Istanbul.