We absolutely love Berlin as a city and highly recommend this apartment if your budget is of concern. Dereks communication was fantastic before and on arrival;even helped with a few things whilst we were at the apartment. However, he stopped responding after the first couple days and despite a few messages didn't hear anything back until leaving.
As for the apartment itself, it is very spacious, airy and has almost everything you need. The beds are comfortable and they can be moved which was great for us. However the kitchen upon discovery wasn't as clean as how it appeared with some dirty dishes in the cupboard and the oven wasnt clean at all- with a dirty baking dish inside. The kitchen doesn't have the widest range of utensils/ crockery either- but has the basics. As for the location. It is very very close to the U-Bahn- in-fact less than 5 minutes away. It is on the main line. The area 'Lichtenburg', was not very nice and wouldn't be visiting unless it was for this apartment.