We had a nice stay at Erna's apartment in Pankow. The apartment was really clean and modern. We particularly liked patio for dining al fresco! We really like the area; it's right across from the Buergerpark, close to great cafes (Stueck vom Glueck is our favorite) and convenient to the S1 and S2 lines to explore the rest of the city. Our kids would add that there are a number of great playgrounds in the neighborhood, too!
For those not familiar with Berlin, Pankow is on the flight path to Tegel airport, so there are planes overhead during the day. The windows on the apartment are very good; it wasn't a problem for us. We really like Pankow because it's just outside the tourist circuit (though close enough when you want to get to Mitte), so you feel a bit more a part of the real Berlin.