Katarina's place is a professionally managed, clean AirBnb in a great location! We walked to Brandenburg gate, Potsdamer Platz and Checkpoint Charlie - all within walking distance.
The apartment itself is lovely with big glass windows. There are 2 bedrooms connected by a corner balcony and one bathroom. The living room is nicely sized, there's a good sized kitchen and a dining area with seating for 8 or more.
We were traveling with a baby and Katarina arranged for a baby cot (crib) as well a feeding chair, which was really sweet of her. The apartment is quite child / kid and baby friendly.
We were able to check in late (post 6pm) by contacting the office beforehand. We were also given the choice to leave our luggage at the office after check out (which we didn't need to ultimately). Note that the office is a 5-7 min walk from the actual apartment, so if you're traveling with a lot of luggage, it might make sense to take a cab directly to the apartment with the luggage and one person go pick up the keys from the office. We had to lug our huge bags from the office to the apartment, and while not too far, that was entirely avoidable.
Overall, great value for money considering how big the apartment is and how close it is to many of the tourist attractions.