I always head for Vivoli for Gelato which is directly across from Santa Croce and down Via Torta one block to the first street then right. The address is Via Isola delle Stinche 7r. They have the best gelato in Florence, in my opinion, so this is a must stop on your trip!! I was first there 30 years ago. The chocolate hazelnut and the amaretto are worth the trip to Florence.
Obika: I liked the décor of Obika which is in the Palazzo Tornabuoni at Via Tornabuoni 16. It has a Mozzarella Bar and Pizza and other specialities in a sleek atmosphere. The Palazzo Tornabuoni is a private residence club with beautifully furnished apartments which I toured in 2007. The original palazzo was built in the 15th century.
Trattoria Sostanza: I was there years ago and loved the old atmosphere of this trattoria, at Via del Porcellana 25, which opened in 1869. I went back for one of the two dinner seatings where you sit at long communal tables. The cuisine is definitely comfort food. The veal stew with beans and the chicken in butter were really good. I enjoyed my dinner companions who were a young couple from Portland OR. You will find more tourists at the early seating and more Italians at the second.
Trattoria Coco Lezzone: I enjoyed a casual meal on my last visit at this very traditional trattoria at Via de Parioncino 26r.
Golden View Open Bar: I went for the second time to this sleek, contemporary restaurant across the Ponte Vecchio and left on Via de Bardi to 58r. Here I had a seat at the window/balcony overlooking the Arno and the bridge. They have three attractive dining rooms each with contemporary art and a nice bar area. If you just have time for a coffee and pastry their Café next door is also really attractive and fun.
Venchi for chocolate or gelato is also a must. Vicolo Calimaruzza 18.
Also, while shopping or after seeing great art, Caffe Pontevecchio, just over the Ponte Vecchio is one of my favorites for coffee or ice cream.
Other restaurants to check out include Trattoria Parione, Buca Orato and Carrillo recommended by my hotel. io Osteria Personale de Matteo Fantini on Borgo San Frediano 167 was recently featured in the New York Times as was Tamero Pasta Bar at Piazza Santo Spirito 11r. Cantinetta Antionori also comes highly recommended. Piazza Antinori 3.