We stayed at the Hotel Lungarno (booked through Amex FHR) in August 2011. We would recommend the hotel - while rooms are small (we had a small upgrade from the entry level room for a better view right on the river), the bathroom is lovely, and the staff is excellent. Breakfast was included and quite nice - a few hot items, lots of fruit, cereal, pastries, etc.

The big draw is the location right on the Arno and easy walking distance around town. Right on the street itself there are a few good restaurants and it is quite safe and easy to get around Florence from there. Hotel staff was exceptionally helpful in confirming reservations and even holding luggage for us - we stayed a few days, left to go to Venice for an overnight mid-trip and returned to the Lungarno for the rest of our stay. My only (small) complaint is that the hotel was not busy during our trip, and we returned to the same room after our overnight in Venice - so it was not necessary for us to pack up and store our luggage. We should have requested to just leave it in the same room since it obviously remained unused in the 1 night we were gone.