I had a great experience staying at Fernanda's house and I would highly recommend it. It's located just a few blocks from the train station and close from everywhere (Uffizzi, Santa Maria del Fiore, etc). The apartment was spotless and my room confortable, clean, well decorated and with air conditioner. My Florence experience was enhanced by staying at such a nice place.
Fernanda is a great host, she replied fast to my questions before I arrived, she was very welcoming, she provided me with a map and show me different places I should visit and gave me useful advice. She recommended the restaurant downstairs, which was actually excellent and very cheap. She would provide you a voucher to have breakfast at a nice coffee shop across the street -I went there with a friend who was not staying with me at Fernanda's but she was so kind she offered to cover his breakfast too.
What else can I say? If I went back to Florence (which I hope I do) I would definitely try to stay at her place again.