Just one word: great. First of all, it is extremely close to the center of Prague (15min by walk, but you also have a metro station and a tramway stop nearby.) and just next to a park where you can chill or have a picnic. Second, the tenants are very welcoming and available to give you any advice or some directions by chat (they lent us a guide book and some change for the metro). Finally, the flat is great with all necesary appliances (microwave, oven), a clean bathroom and a lightful living room.
There is simply everything you need for the perfect stay in Prague.