We stayed at the Sara's place for 4 nights. We arrived at 10 pm, but the check-in went smoothly (took a key in the nearest shop).
The flat is spacious and comfortable with a large living room, separate kitchen (with everything you need), bathroom and toilet.
The location is simply great. On the one hand it is really close to the city center (tram stop in front of the house or about 10 minutes walk to the Charles Bridge, 4 minutes walk to the Petrin funicular). On the other hand the flat faces courtyard and green gardens of Petrin hill, so its really quite.
We can highly recommend Sara's apartment!