I'm not good at writing these reviews but I'll give it a try.
What I liked
The apartment is immaculate. Very nice and well kept. It's within walking distance to the train station that can take you to directly to the Brandenburg gate and other attractions. Also within the vicinity the train station, there's plenty of shops, restaurants, clubs. Carsten is a excellent host. He met us when we arrived, showed us around and directed us on where to go for the sights, and restaurants.
What I did not like.
There isn't much to not like. The only thing I can think is there is no elevator in building where the apartment is located. If you have heavy luggage, be prepared to go up 5 flights of stairs. You will get a workout. The other thing I didn't like is the parking situation. If you are driving, when you find a spot, just leave the car and walk. Everything is definitely within walking distance. Probably one suggestion for Carsten is to draw up a map of the immediate area and show were the driving guest can legally park without risking getting a ticket.
Overall I would use Carsten's place again if he would have us..