We had a pleasant stay overall. White River Srl were very communicative, replied quickly and were flexible with check-in time. The area around is very nice, vibrant and close to many of the city's main tourist attractions and restaurants.
However, we encountered a few problems during our stay, somewhat diminishing our experience. The boiler wasn't working properly upon our arrival, and I didn't know how to fix it since I have no experience with such boilers, resulting in lack of warm water in the shower until the second day, when I worked out the problem mostly by myself (the owners helped by sending instructions, but I ultimately fixed it myself by reading the manual and looking online).
The biggest problem was the mosquitos - I realize this is a general problem in Florence, but I suspected there were much more then there should be, and visiting other apartments and talking to locals confirmed it.
Overall we had a good time, hopefully the problems would be mitigated.