I highly recommend staying at Rasim's hotel.
Location: Right off the coast of the Golden Horn with a wonderful view of the river. Of all the neighborhoods i saw behind the Walls of Constantinople, Balat seemed like the least redeveloped. Just roaming around the neighborhood will fire up the imagination. It is mostly off the tourist track, but feels very safe and offers all the amenities one could need. Ideal for walkers but not the best situated for public transit. But the busses that rides along the coast will at least get you to a transfer. Do yourself a favor and stay in Balat.
The Room: Exactly as pictured. Clean and comfortable. The picture of the view doesnt do it justice, you've got an impressive panorama.
The Service: From booking to leaving, Rasim was incredibly helpful. Adresses in Istanbul arent very useful, so Rasim had me call him to give the taxi directions. He helped with any questions and really went the extra mile to make sure i got what i needed. Top knotch service.