The flat is great for short and longer stays, I would definitely return. It was clean and tidy, and the hosts' arranged a later check in when my flight got delayed. Overall, the hosts were very friendly and accommodating!
The location of Radek and Marsella's flat is great. The neighbourhood is buzzing with activity during the day (brunch places, a farmer's market, ...) and quiet at night (perfect for a good rest after a day of sightseeing). It is also very well connected to the Old and New Town. A couple stops in the green line will get you anywhere, the metro station being a 5' walk from the flat is very convenient.
Overall, it was a great stay in Prague!