I stayed with my friend at Parvin's place for the first 4 nights of our stay in Istanbul. We picked Old Town for the start because it's where most major attractions are and we wanted some time to get used to how things work here before moving to other parts of the city. I highly recommend this, it worked perfectly for us.
In addition to its proximity to historical destinations, the hotel is located away from main roads and busy streets. We slept very well (better than I expected) thanks to this. The bed was also comfortable and wifi was sufficient that I could work without problems. We also found some really good restaurants (affordable with food better than some of the 5 star review restaurants we visited later in other areas), despite it being the most touristy area.
Parvin was very attentive and a good communicator. We didn't have much to ask but he'd be more than happy to help with any requests. The lobby is attended 24 hours a day and we walked back to the hotel every night without any issues at all.