My wife and I spent 6 nights in this apartment. Here are the positives and negatives of the place.
Good points :
Auto check-in works great. Also, we were arriving early in Berlin and Sören agreed to let us check in early. Thanks Soren.
The apartment itself is in a very nice area. There are many restaurants within walking distance, grocery stores, bars, etc.
If you like to walk, in about 45 minutes you can walk to the centre. Anyway, the metro station is very close, so it's very easy to go anywhere in Berlin.
In other words, the location of the apartment is perfect.
The apartment is well equipped for cooking, washing your clothes, etc.
Negative points :
The apartment is smaller than it looks from the pictures.
There is no closed room, everything is open.
The wall directly adjacent to the street is a window. The curtains must therefore be closed all the time otherwise people can see you from the street.
There are no other windows in the apartment and the air conditioning is stand-alone (no heat exhaust outside) so ventilation can be a problem. The week we spent in Berlin was not too hot, so we did not suffer from the heat.
There was no soap, no shampoo, no coffee available when we arrived. I always appreciate when these are available for a day or two.
Would I go there again? Probably, surely, if a few of these issues would be resolved.