This a great studio apartment in a nice location. Charlottenburg maybe isn't quite at the happening heart of the city, but it's a pleasant and fairly quiet area which is good if you're needing a good sleep. I used it as my base for running the Berlin Marathon, and it couldn't have been more perfect.
The location is about 10 minutes walk from either of two U-bahn stops and there are a few decent restaurants nearby. The apartment itself is a simple, perfectly clean and modern studio, with a small kitchenette and shower room. There's a king size bed with a nice soft mattress - it might not be supportive enough for some tastes, but after a marathon it was just what I needed.
I didn't get to meet Ulrike in person, but she was very communicative, and even helped me improve my German through her messages! Key pickup was nice and simple too. All in all, it was a very pleasant stay, and one I'd highly recommend.