The place itself is beautiful, located in quiet neighborhood close to historical places you are going to visit. The service is outstanding! Yusuf and the team are truly the best hosts! They do care about guests, they help and make sure you're fine, and at the same time you have and feel your privacy. Yusuf will give you the map and explain what to visit better, how to get there, where to eat etc. The coffee downstairs is great. The roof terrace is a nice place to have a glass of wine in the evening or a cup of coffee in the morning. Definitely will stay here when we're back to Istanbul.
Also, ask Yusuf to call a taxi to pick you up from/to airport. It's twice cheaper than you'll get yourself if you don't speak Turkish. However, if you prefer public transport, it's easy to get there by M1/T1 lines with just one crossing.