I highly recommend Seren's place. The room is clean and spacious. It is located on the ground floor and has a view to the street. There is all-day access to the rooftop terrace, with a gorgeous 180 degree view of the Bosphorus. Just 5 minutes walk to the Bosphorus, and 5 minutes walk to Taxim.
Seren and her brother Altay also stay at the apartment. Altay has a separate bedroom and Seren sleeps in the living room when a guest is there. There are no pets. When I was there, Seren was out on holiday, but Altay went out of his way to make me feel totally at home. I will always choose Seren and Altay's place whenever I visit Istanbul :-)