Karina's place is located in the heart of Friedrichshain and is very close to many restaurants and bars. It is no doubt a wonderful location for tourists. One major hiccup for me was the key handover when I was checking-in. Karina did not mention that I may have to go to her friend Ada's shop nearby to pick up the keys. This was a last minute shock for me after traveling for more than 15 hrs to a new city with two big suitcases and not being able to communicate with my cab driver in German to switch my destination. Other than that I think it is important to note that this apt is on the 5th floor and there are no elevators.
The apartment is beautifully decorated, has a lot of privacy and is big enough for a couple. I would recommend this place for short stays. It is very close to the tram stops and the subway is 10 mins away. There are many grocery stores, bakeries and pharmacies near by. I did not have many problems with the apartment after I had settled in for my month long stay.