Me and my kids had a nice stay in the apartment which looks beautifully stylish and was very clean. The apartment is in a nice old building which also hosts a youth hotel. When we were there it was extremely quiet and no noise or whatsoever from other guests. The Crellestreet where the apartment is located has a nice ambiance with lots of small restaurants and cafes. U-bahn station is a convenient 10 min walk away, from where you can reach most destionation in Berlin city in 15 minutes.
One thing to may want to take with you when you are used to sleep in very darkened rooms are eye shades. Part of the stylishness results from the blinds in front of the windows. In the entire building. Nice, but not so good in keeping sunlight out in the early morning :-).