A good apartment in a good location. It's a bit basic but if all you want is a base to explore Berlin from then it's perfect. If you're expecting a home from home then this isn't the apartment for you.
The Brandenburg gate, Bundestag, Holocaust memorial and Checkpoint Charlie are all in walking distance. Other sights are further away but the public transport in Berlin is great so it's easy to get to them.
There's a supermarket across the road and a few decent restaurants nearby, but it is quiet in the evenings.
Communication with Heinz was good, the check in & key collection went smoothly. Overall we had a good break.