My wife and I stayed at Modestino's place for 2 nights and it was an amazing experience. It is a full, nice-sized flat in a great area across the river from the more touristy areas of Florence. It is a short walk to Piazza Santo Spirito and the restaurants/nightlife that surround the piazza. It is an easy walk (maybe 10 minutes) to get to the other side of the river to the top tourist attractions, making you the perfect location to experience everything Florence has to offer.
The flat itself is charming and quite large with a living space, kitchen and larger bedroom. Everything was very clean upon arrival and they even provide you utensils and cooking supplies if you want to do a little cooking (we chose not to based on our short stay). There is a nice terrace area that overlooks a quiet courtyard. The terrace was a great place to wind down after a busy day with a glass of wine and a book.
The hosts (we met Emma) were there when we arrived and provided a lot of helpful suggestions and answered any questions we had before she left. They were very communicative throughout the process and I would definitely work with them again. All in all a great space and a great host!