We had a great experience at Ekaterina's apartment. The flat is cosy, very clean and quite spacious. It has almost everything you may need for living. The only thing missing is wifi (but we've solved the problem with free wifi outside the building).
The location is perfect - 2 minutes walk from S-bahn station (Zoologischer garden), which is in 3 stations to Hauptbahnhof. Zoo is just 5 minutes walk. The neighbourhood suggests a great variety of good cafes and restaurants. Supermarket is also very close (located at the S-bahn station).
Communication with Katy was very easy and she was very nice and friendly.
Totally recommended for a stay!