We loved staying at the apartment. It was very convenient to all the attractions on offer in Florence. Close to the main train station and Santa Maria Novella is just around the corner in front of a lovely square. From that square you can see the Il Duomo, which is only 10 minutes further. Plenty of restaurants along the street. I would recommend La Grotta Di Leo. We were met by Costanza who was very nice and helpful.
Yes, there are a lot of steps up to the 3rd floor apartment but you will be walking everywhere in Florence anyway so you will need to be fit.