Get thee to a nunnery! This apartment is in an old convent, which explains the interesting courtyard entrance. First things: don't bring big suitcases here, as you will never get them up the VERY tight spiral staircase that goes up two flights; also, don't be too tall, as I am six-foot (183 cm) and that is close to the limit if you don't want to duck in a few places. Of course, that is true in many places in Florence (Il Duomo)!
The apartment was very neat and clean, but furnishings are probably 25 years old. The bed is a little worn, and I "sank" into it. Be sure you are very intimate with your travelling companions, as there is no privacy in sight or sound (pocket bathroom door and zero soundproofing). There are instant coffee and some breakfast biscuits, which is very nice.
The best feature is the convenient location, with "our" church square (Basilica di Santa Croce) a great landmark (you can easily pick it out from the top of Il Duomo) just two blocks away (a right turn when you walk out, and then your first right). Walk south of the piazza there to Via dei Neri and turn right (west) to get to the best panini shop in Firenze (my opinion, look for the lines!) All'Antico Vinaio and have a 5 euro panini that will feed two!
Walking to Il Duomo, La Accademia, etc. is all very easy, you are just blocks from the river, and there are restaurants, shops, and bars within a few blocks. The place is a little hard to find, as the street numbering in Florence is crazy (red and blue numbers that often aren't in sequence), but bus C2 drops off pretty close. A solid, if not glamorous, place to stay.