For the price we got the rooms, it wasn't terrible. Rooms are spacious, clean, and well appointed. Location is good, and it is certainly a real hotel with amenities, not a small operation like most Istanbul places seem to be.
But for the price, and for what they are going for with the hotel (down the street from the Peninsula...), the service is so-so, and the noise issues folks have mentioned in other reviews are real. Our room on a lower, street facing floor had significant noise from the street restaurant until quite late. Our room on the top floor had noise until well after midnight from the rooftop restaurant- the nearly constant sound though the ceiling of people shifting their chairs on the floor upstairs. For a hotel at this price point, aspiring to what it does, this is unacceptable and makes for a bad night's sleep if you want to go to be early or don't have earplugs.
Also, the pillows are among the lumpiest and hardest I've ever encountered at any hotel, no less one like this.