Our gang of three couples spent four nights at Oliver's place and truly enjoyed it. Location is great; Friedrichshain's cafeterias, restaurants and bars just behind the corner, walking distance from Warschauer Straße U & S Bahn stations and Tram line where you can travel pretty much everywhere.
Check-in, check-out and overall communication with the hosts went super smoothly. The huge two bathroom apartment with separate bedrooms was perfect for six of us. Plenty of room to just to hang out and have a good night sleep, and the modern kitchen made the breakfast mornings really easy for us.
Definitely will book this place the next time when we come to Berlin with crew this big.