I am a bit late on commenting on this - I wasn't really doing much blogging over the summer when I think it finally went live. So - if you are in the dark too - the Firenze Card is Florence's attempt to catch up with many other major tourist cities by offering a product that makes it easier (and ostensibly cheaper) to get into museums/sites etc. and also gives you a transportation option (not that that is so necessary in Florence, where almost everything is within walking distance for most).
Their website has some quirky translations, but looking through it and seeing what is offered I would have to say this card is a major win. The list of 50 places you can visit is impressive (although some of these are free already and open only limited hours), and the free bus rides are a great kicker for the few spots not right in the center.
The only issue I can see is the price, as it can start to add up for families that are not EU citizens (EU citizens get one under 18 admission per adult card). At 50 euro per person, if you have a few kids and are coming from the U.S. or other places outside the EU, it could sound expensive - especially if you only visit a couple of places. I would prefer to see a card like this either offer the same discount for everyone with children under 18, and also last longer than 3 days - 5 would be optimal. But those are quibbles - overall if you want to visit a lot of museums and churches, and not have to wait in line or make reservations, this is an awesome new option.