We enjoyed our stay at Guido's place! It is in the center of the city and everything is basically within walking distance. Side note, expect that in Florence; lots of walking. Public transportation/uber/taxi is not really a thing here.
The biggest thing to note is that the unit IS on the 4th floor (Guido does tell you this in her description). If you're out of shape, have knee, foot, or back injuries, or have extremely heavy/ big luggage I would not recommend it. The stairwell was probably the most narrow out of the homes I've stayed at but it was only rough the first day because of our luggage (we were visiting multiple countries on this trip so we packed a lot). But after it wasn't so bad on a daily basis.
The home is very spacious. This was my favorite bathroom from our trip because it was a large shower (compared to the others/ or they didn't have a shower) and the water pressure was fantabulous. Guido was also quick to respond when the bathroom light went out. We didn't use the kitchen much (the stove) but we did use the washing machine. Guido even has a drying rack, iron, and ironing board in the home for use.
A couple things to note: 1) Since it is in the center of the city you will hear the nightlife. It's not too bad but if you're a light sleeper it might be annoying. 2) It gets chilly. She does have a heater in the closet but it looked too intimidating to figure out, but in the same closet she has a lot of spare blankets so we used those. During the spring/summer it'll probably be nicer. 3) The bed feels like twin beds put together on the bed frame. It is large enough (queen size I think) but if you're a picky sleeper it again might affect you.
Guido was a great host. She sent information a week prior to our stay, and a couple days before, and on the day of she made sure we got in okay. In the home brochures on activities to do, a map, and a binder explaining the house stuff were laid out on the desk. When we had the light issue she fixed it the same day while we were out. When we had to check out, she set up a taxi for us to pick us up. Thank you for your hospitality Guido!