Albert was a fine host and we really enjoyed the 10 days we stayed in the apartment. The space was very clean, Albert offered useful tips about dining places in the vicinity, guidebooks for Berlin, and a binder with information in German and English about the appliances in the house (dishwasher, washing machine, air conditioner, and the TV). And when we left, he checked us at 5 am on a Sunday so we could reach our early morning flight.
We had no issue with that, but it should be mentioned that the apartment is on the 3rd floor (no elevator), and that it is located about 10 minute bus ride from Ka De We and 15 minutes from the transportation hub in Zoologischer Garten, and that it takes about 30-40 minutes to travel to tourist attractions around the area stretching from the Reichstag Building/Brandenburg Gate to the Museum Island or Alexanderplatz.
The apartment's neighborhood is a quite residential area (the apartment itself sits close to a main street, but the windows are very good in keeping out any noise). We loved the fact that it is only 5 minutes walk from Viktoria-Luise Platz, and even more so that it is only 8 minutes of leisurely walk away from Goltzstrasse (great variety of tasty 'international' foods like Vietnamese, Indian, Persian/Iranian, Italian, Burgers, etc.) and 10 minutes walk away from Nollendorfplatz (more dining possibilities, including Turkish and Greek restaurants and a falafel place, to name a few). 2 minutes from the apartment there is a small Edeka neighborhood grocery store.
To sum it up, we stayed in the apartment for more than a week and enjoyed its cleanliness and amenities, the non-tourist trap ambient of its neighborhood, the great dining options nearby, and the reasonable time it took to travel from there to tourist attractions in Berlin through public transportation.