We loved our stay at Ingo's apartment very much. The place has a soul, as you can see from the photographs – there are a lot of photos on the walls, posters, several musical instruments, lots of other interesting stuff. It is also spacious (easily accommodated 4 people), clean and well-located. A tram stop is 2 min away and in 5-10 min you can reach a subway station, from which it is only a 20 min train ride to the most touristic places in Berlin. There are also lots of bars and restaurants nearby, but the apartment is located in a quiet street.
We didn't meet Ingo (we were greeted at the apartment by Penelope), but communication both with him and Penelope was very easy. Ingo was also very adaptible regarding our check-out time.
P.S. There were a couple of small but very nice things that made an impression on us. First, this is the first AirBnB apartment in my experience that provides the means to prepare your morning coffee in 4 different ways: with an espresso machine, drip coffee maker, french press or a moka pot. As coffee lovers, we appreciated this very much :) And second, all essentials, such as toilet paper, paper towels, dishwasher tablets, and even some non-essentials that we didn't expect, such as coffee, tea and cooking oil, were provided abundantly – some AirBnB hosts try to save money on every trifle, so that eventually you end up buying half of the stuff yourself, but this was not the case here :)