My partner and I loved staying at Yusuf's! The facility is called Cube Suites, so it is best to use the address that comes up on Google to give to taxi drivers for ease. The front desk is staffed 24 hours, so there was someone to welcome us even in the wee hours of the night. The staff themselves were warm and welcoming, always greeting us with "how was your day?" They are keen to provide information on the best way to cover all the sites of interest, as well as food suggestions!
The location is ideal, only 10-15 mins away from Hagia Sophia, Blue Mosque, Topkapi Palace and the Çemberlitas tram station. Also 15-20 mins away from the Grand Bazaar, Spice Bazaar and Galata Bridge. The unit itself was clean, well-furnished, and cleaned daily. The small downside was we came in winter and the unit was a bit warm from the centralized heating system.
Overall though, we had great stay at Yusuf's and would definitely recommend!