One of the best places I've stayed while abroad, including hotels. The space is great and kitchen and bathroom well-equipped and clean. I had a very pleasant stay and can definitely recommend to anyone who's coming to Berlin.
Restaurants, stores, etc. are within close walking distance, and the touristy stuff like the museum island is but a 15-minute walk away.
There is an aquarium in the room with an air pump going all hours. Personally I had no issues with this, but if you need absolute quiet when sleeping you must bring earplugs.
The only thing I can complain about is the state of the aquarium: overgrown with algae and only one living fish. Other than that, everything was good!