Karen is a wonderful host. He was always easy to contact and eager to assist and answer any questions.
The apartment is extremely well positioned, with great cafes (we particularly recommend Wine Time) nearby as well as a couple great museums.
The only negative moment we could notice was the flat not being particularly tidy - nothing criminal, mostly dust here and there. Karen assured us he would soon switch his cleaning lady in favor of a more thorough one. Also, the bed wasn't particularly comfortable and a bit short for my 185cm height.
We would recommend you to contact Karen a day or two before your arrival in case of your visit in winter. We failed to do so and Karen thought that we would be cancelling our trip. Because of that he had to rush to the apartment to launch the heating which took another day to warm the flat completely.
Overall, the flat is definitely worth its price - it is spacious, comfy and well situated. We would recommend it to our friends for sure.