re: Florence dining recs?

Buca Mario - straightforward Italian with very good food.
La Sostanza - if you want bistecca Fiorentino, go here. Two seatings a night, most at a community table. Fantastic food, even better experience.
Cafe Nerbone in the Mercato (the covered market) - think of it as a plate lunch type place. Awesome ribolita, sandwiches, tripe, etc. Cheap and very good.
Cantinetta Antinori - the restaurant of the Antinori family (the Mondavis of Italy). Really good food and all the Antinori wines are offered by the glass. The Frescobaldi family has a similar set up which is also very good.

There are others, but I've been to all of these multiple times and had very good experiences.