We stayed at Dina's spacious apartment with our 4 month old. It was really great to have a place that (a) had an elevator and (b) was a fairly short bus ride away from the Zoologischer Garten station. Note that there is a half-flight of steps from the elevator to the apartment. Our stroller was fairly light so it wasn't too much of a problem.
The apartment building is right on the water, so we really enjoyed our walks in the area. There is an Edeka quite close by, and few restaurants (not a ton, but enough variety for a short stay). Overall, we were quite happy with the apartment. :)