We had a very pleasant stay in Berlin in this apartment of Henrik and Sven. Sven received us, was very friendly and gave all the information we needed. The apartment was clean, bigger than appeared on the pictures and had comfortable beds. Location was perfect. Prenzlauerberg is a very nice neighborhood to stroll around, to eat and drink and have a Fruhstuck. It was nearby a subway station. We also got two pairs of keys, which can be very convenient.
Downsides: som small ones: the apartment is a holiday apartment, so it lacks the typical feeling when you rent a normal apartment on AirBNB. And in Summer you may miss the option of a balcony.