The apartment is located in an area that is close enough to major attractions to be able to walk, and far enough to get a good feel of the vibe of ordinary İstanbul. The rooms on the front have a great view on the street and neighborhood and get a bit of the hustle and bustle in (enough to know you're in the largest city of Europe, but you're high enough up to let you sleep at night) and in the master bedroom in the back you will only hear chickens and seagulls (and the omnipresent calls to prayer).
The apartment is on crawling distance from the lively fish restaurants of Kumkapı. If you like fish and live music then this is the place to go. There's a good pastanesı on the corner to fulfill your morning coffee needs with some delicious Turkish sweets.
The appartment has a spacious seating area, that is sheltered from the summer heat. The bedrooms are functional (as long as your suitcases aren't too big), the shower is great (especially if you just ran the İstanbul marathon), and the kitchen is tiny – but you don't want to cook at home in İstanbul anyway.
The area north of the appartment is all pedestrian zone. Make sure your taxi driver is aware of that. Ours brought us from SAW airport and made us walk a long way (that's the taxi's fault, not a problem of the appartment). If you walk eastwards (towards Sultanahmet) you will usually pass a taxi real soon. So if you want to go to other areas of İstanbul (Golden Horn, Beyoğlu) without figuring out public transport then that is quite easy too.
All in all our family of four (parents and two students) really enjoyed our stay in the appartment