I stayed one month at Stefano's place. He is just the very best host, and his place is stylish & clean. Location is also very good. But most important is his hospitality and communication (both before and during the stay). He is very careful about details, thoughtful, helpful, respectful ,... . Generally I do not feel myself comfortable, when I just rent a room rather than the whole flat. This was not the case this time. I definitely felt myself comfortable during this long stay. And it is basically because of Stefano's hospitality.
About the location of the place: it is very close to S-Bahn & U-bahn (5-6 minutes walking distance), And then in 6 stations, you may arrive to Berlin central train station. Or, central places of Berlin like Alexanderplatz and Friedrichstrasse are even closer to the house, than the central train station. You may even go to these central points by bike as well (as I have done).
About the room: The word "comfort" depends on person and expectations, and the expectations have no limit. But, this room, and generally this flat is definitely more than enough! If your expectations are not on the moon, then I believe that you will feel yourself comfortable. This room is normally the living room of Stefano's flat, which is large and very cosy. And since it is normally a living room, there is not a bed in the formal meaning. There is a very comfortable sofa, which is also very comfortable for sleeping.
I definitely recommend a stay in Stefano's place!