Andrea's place was excellent and we definitely recommend it! It is conveniently located about 10 minute walking distance from the main train station, and includes all the amenities needed for your stay. We loved that it felt homey like someone could actually live there rather than like a hotel room. The check in process was easy and Andrea responded promptly to my messages when we were running late due to train delays.
The unit is about 10 minutes walking distance from the Duomo, and from there we were able to walk and explore various parts of Florence with no issues. In regards to the unit, it is located on the top floor of a walk-up only building (no elevators). The stairway gets somewhat narrow, so you may find it difficult to carry really large/heavy luggage up those stairs. Also, the unit is above a very popular restaurant and across the street from a large market, so you'll hear delivery trucks early in the morning and dinner patrons later in the evening.