Out of all the places I stayed on my Euro trip, Hotel Cestelli was by far my favourite. While the rooms are basic in their amenities (especially if you book the shared bathroom option), they are more than worth their great price, and have plenty of character. The room was quiet, clean, and had a classic European flair that my travelling companion and I simply loved.
The best part about Hotel Cestelli wasn't the room though, but rather its hosts Alessio and Asumi. Not only were they very kind in allowing a late check in and holding our bags on our checkout day, but they were simply kind and helpful people. Alessio in particular has a clear love for his city, and literally took out a map and recommended not only the best sights, but also amazing restaurants that most tourists would usually never find.
If you're travelling to Florence on a budget, do yourself a favour and book with Hotel Cestelli.