The apartment is lovely - spotlessly clean and stylish. It's smaller than it looks in the photos, but there's still plenty of room for an enjoyable stay for a group of friends or up to 3 couples. It's in a great location; easy to reach all the major tourist sites on foot, and not on a main road, so not a lot of excess traffic noise.
Alex and Kate are exceptionally helpful and very quick to respond to messages. They gave us recommendations for public transport and lots of handy hints for things to do and see, places to eat, and the best Christmas markets to visit in the city.
The only downside during our stay was a refurbishment taking place in the apartment next door, from early in the morning until well into the evening. But we spent most of our time out exploring Prague and so it only bothered us each morning when the noise woke us all up. The refurb will probably soon be over and I'd undoubtedly recommend this place to any visitor to Prague.