In short, you can find a much better place to stay in Istanbul for less than half the price. My grievances are below.

1) I'm used to tight spaces and even showers located in bedrooms, but if you're paying 110 euros a night for a room, then you should spruce up the accommodations a bit. Since the showers are located in the rooms and right next to the beds, the steam and condensation makes everything in the room very damp and cold -- despite the heaters. Every night, the sheets were so damp that I had to lay blankets I bought at the market on top of the bed to lay on. If you like breathing thick and damp air 24/7, then you won't have a problem.

2) The location of the hotel is great and the staff, at first, are very friendly, but if you're looking for a place for a longer stay with more flexible accommodations, then this is not your place.
We let the owner know 3 days ahead of time that we were planning a trip outside of Istanbul and would like to cut our stay short. His friendly demeanor was dropped and he was incredibly unprofessional -- instead of being like the owner of a boutique hotel, he was unreasonable and told us to leave the hotel immediately. At first, I was very sympathetic with him, and we let him know that we would be willing to pay for the days that he was unable to book a room for, but he refused and demanded that ALL the money be paid.
In fact, his cancellation policy is the most unreasonable I've ever come across, so be sure to read it carefully. Even if you cancel 30 days ahead of time, you are expected to pay 25% of the total price.

3) He demands that cash be paid up-front and in full. While this is understandable on the surface, he is not a licensed hotel and therefore you have no rights as a patron. If something goes wrong, he does not have to give you a refund for dissatisfaction. He does not advertise this on his website and I'm sure we were not the first to be surprised that we would need to extract over a thousand dollars in cash and pay him -- with no way to get a refund.

4) We booked our stay of nine days online, thinking that the increased room rate over New Years would decrease after New Year's. Instead, the rate conveniently dropped on January 7th -- the last day of our stay.

5) The "common" area is not a "common" area at all -- it is locked during the day and night. The same is true with the kitchen. There is no area to sit and relax besides your own room.

I recommend the Buyuk Londra for a nice stay. While many have complained the unrenovated rooms are musty, they were not damp and the service is unbeatable.