I stayed with my family (6 adults) at Sarah's place and my favorite aspect of it is the LOCATION of the apartment. It is facing the Charles Bridge and you can walk to most tourist attractions from the apartment. Also, there are many restaurants and eateries within the vicinity that you can choose from. You will be spoilt for choice.
Communication with Sarah was excellent as well. On the first day, during check-in, she gave us a very detailed introduction to the apartment. She explained all the locks and amenities in the apartment. Also, when we encountered an issue with the hot water in the bathroom, she rushed down to the apartment within 20 minutes to help us out and the hot water / heater was back up and running well.
One noteworthy point is Sarah provides a book in the apartment (which she typed and printed) which details all the recommended eateries and places to visit while vacationing in Prague. She also indicates the do's and don'ts in Prague which was very helpful!
The apartment is very spacious and each bedroom has an attached bathroom. So, it is very suitable for large families to stay together.