I would definitely recommend this place. The apartment is clean, spacious, and well stocked with essentials like towels, soaps, pots, plates, etc. The beds in the loft and main bedroom were comfortable. We didn't use the couch bed. Note that there is a key that you use to sort of turn on the electricity (e.g. the lights and Internet won't work without the key in) but the washing machine DOES work without the key so you can leave your clothes to wash while you are out.
It is in a very convenient location near several of the major sights and the train station. Every day the street below the apartment becomes crowded with tents of people selling things (mostly leather goods) but it didn't cause any problems for us and was enjoyable to watch. The Central Market is on the other side of the street. We didn't go to the ground level, but the 1st level is open late into the night and is a sort of upscale food court.
Guglielmo was very kind and helpful. He helped bring our luggage up the stairs (no elevator). He showed us maps and where we were and where to go. He showed us around the apartment and answered all of our questions. He even gave us extra time to check out when we misread our checkout date and were still sleeping when it was time to leave! He is a very good host.