Sven was a great host for us.
we stayed in the flat for 5 nights and had a good time.
Check-in was quick and the woman waited for us when we got from the airport.
There is U metro station 2 min walk from the flat so you can get fast to any point in Berlin.
I recommend Sven flat for staying in Berlin.
One note you should know, the curtains aren't really dark so lights come through the windows in the mornings.