I went to Istanbul December 2008 and was booked to stay at FS in Sultanahmet for the duration of the stay (7 days). We noticed at the front desk that we could divide the stay between Sulta.. and Bosphorous. After two nights, we decided to give the Bosphorous a try. So the idea of dividing the trip between the two FS is smart.

Review of Sulta:
It was a great hotel, but be aware that the hotel was formerly a prison (only if that stuff bothers you).

Spa lacks, but thats what you have the other hotel for.

Breakfast was good, but the eggs consistently tasted funny (at both hotels). I don't think I've ever had more smoked salmon in a week.

Room was starting to look a little tired. I don't know if they have updated since).

Review of Bosphorous:
Beautiful property, great bar, nice bathrooms in the room.

The nicest breakfast buffet. They had amazing flat bagels (which were perfect with cream cheese and smoked salmon). Delicious fresh orange juice.

Beautiful spa, try the traditional Turkish Hamam.

We had dinner at the restaurant one night. I remember the pasta with seafood being very good.