My wife and I stayed at Sultann's Inn during our visit to Istanbul. The hotel is conveniently located in the district of Sultanahmet, just a few minutes away from the main mosques and downtown attractions. Nearest tram stop is ten minutes walking.
Our room was comfortable and clean. At our arrival, we found a complimentary bottle of water in the fridge, fruit and cupcakes. Every morning, a nice breakfast is served at the terrace, where you have a nice view of the bosphorus.
What really set this experience apart was Leo's attentions (Guest Relations Manager), who went above and beyond in making our stay a pleasant one. He was like having a luxury concierge at our disposal. He even contacted a local restaurant so they would bake (for free) some frozen pizzas I bought at the supermarket!
I highly recommend this place for staying in beautiful Istambul if you're looking for a convenient, affordable and friendly place.