We spend a really great time at Carol's place.
The apartment is really close to the Mercato Centrale, not so far from every practical places (Santa Maria Novella train station with train and buses to visits around) and visits places (Duomo, San Lorenzo, etc.)
The apartment is really big and we can also enjoy the balcony outside. It's well equipped with washing machine, kitchen accessorizes, addition blankets if needed, etc.
The only default (not a big one) is that the place is noisy around 7am and 8pm when the Mercato exhibitors get installed or packed up.
We really recommend Carol's place