I stayed with Marco and Christiana for over a month. Both the apartment and my room were exactly as I had anticipated after reading their description on airbnb. Right from the start, Christiana and Marco made me feel at home. Throughout my stay, they were a treasure trove of tips, always eager to help. Both were extremely open and accomodating. Since I attended a language course in Florence, they gradually switched over to speaking Italian with me: this was done solely for my benefit, since they communicated in very good English with their other hosts. They both helped me with my homework, let me use their bike, were extremely considerate concerning my dietary requirements, etc. etc. etc. In fact, I consider them more like friends now than "hosts", and we are still in touch.
The location of the flat is perfect: very close to the station, not very far from the city centre (I walked to my school every morning, just a 15 minute walk to the dome). There are loads of shops and restaurants nearby, and the area isn't as touristy as some of the city centre of Florence. I also enjoyed having a cinema nearby and, since I go running fairly regularly, it's not very far to the park along the Arno where the locals go running ... you can run for miles along the river, which I greatly enjoyed, since it was nice to leave the city behind every now and then.
The area is very multi-cultural. To someone not familiar with the concept of "living" in the street (i.e. convening in small groups and chatting till late in the evening) this might take some getting used to. Also, the single room looks out into an inner court-yard. If you want to leave the window open at night, you should get used to the fact that you can listen in to other people's conversations.
The room has everything you need. Outside the room, there is a kettle to make some tea and coffee and a fridge for the use of guests. Of course, I could use the kitchen, in fact we sometimes prepared meals together and enjoyed each other's company.
At first, I was a bit worried that there would be a queue to get into the small shared bathroom for the guests, but since I left for school before the other guests there never was any problem.
For me, Christiana and Marco were the perfect hosts: there when I needed them but never clingy - I could decide how deep I wanted to be involved in their family life. At the end of my stay, my family came to visit and also got to know the two: I can only highly recommend these hosts, and I will certainly stay with them again at some stage in the future.