We had a wonderful stay at Annalisa & Leonardo's apartment!
The location is absolutely perfect for exploring all of Florence's many sights on foot, as well as being only a 5 minute walk from the Santa Maria Novella train station - which is also a main meeting point for anyone doing an organised day-tour.
(Also, from the airport a taxi took only 20 minutes to drop us in the main piazza and was quite reasonably priced.)
For food and wine Mercato Centrale (an incredible two-level undercover food market) was literally 100m from the front door, and ZaZa's restaurant was even closer - right downstairs - serving the most beautiful meals over lunch and dinner. Best truffles I've tasted!
The apartment itself is small, but beautiful, with incredible attention to detail. It feels both modern and authentic to its traditional aesthetic at the same time. While there are a few stairs to climb in order to reach it (roughly 60) even with two suitcases it wasn't a huge problem - you might even find them welcome to work off those delicious dinners! Leonardo was downstairs to greet us on arrival and was very warm and friendly, giving a full rundown of the apartment and also offering suggestions on where to visit, eat, shop, do some laundry etc. He was also very responsive to any odd questions we had during our stay.
Overall, I would highly recommend the apartment - either for a couple or a pair traveling separately.