Martina's place was a wonderful five nights to start of 3+ weeks in Germany. The location is just about perfect -- in the middle of Prinzlauer Berg's food scene and well-served by tram and U-bahn (I seriously recommend the tram when arriving and departing to avoid having to deal with luggage on stairs and the crowds). It's maybe 6 minutes down a long level street to the nearest M10 stop to the train station, about 3 minutes to another line going to Museum Island. The apartment is one floor up on a wide staircase. Martina was there waiting for us at check-in. Her apartment had a lot of touches and she expertly explained everything in just a few minutes.
The location was surprisingly quiet given the number of restaurants nearby (and realize that Friday and Saturday nights are gong to be noisier than normal, no matter what). the beds were comfortable and we slept very well. The kitchen had everything we needed and the shower had good pressure.
We will be back!