We had amazing 4 days in Prague in the beginning of December. The apartment has a perfect location within 10 minute walk to everywhere. It was very clean and cozy, just like in the pictures (unfortunately without a champagne :( )
The hosts were very professional. We were given a map and some useful information about transportation and some great recommendation about sightseeing, restaurants, bars, etc.
However the room was quite cold, I believe it's because of the windows. They seemed pretty old to us. And thus radiator wasn't enough to warm the room. They have thick blankets but if you're going to stay in here in winter, it's highly recommended to bring some thick pj's to wear at night.
Overall, it was a great place to stay in Prague that we highly recommend!