I posted this on a thread about a year ago but my recommendation stands:

Please check out the Hermitage Hotel:

http://www.hermitagehotel.com/eng_new/about.htm

Nice small hotel, nicely decorated rooms, incredibly nice and helpful staff. Located immediately at foot of Pte. Vecchio, 1/2 block from Uffizi. Nice living room with cocktails/wine available in evenings, view of river and Pte. Vecchio. Breakfast on the roof every morning. We had a wonderful stay there last fall and will definitely stay there again when we return to Florence (hopefully soon)!!