If you buy a Firenze Pass, I understand it covers admission to the Academia, Ufizzi, and other museums. However, do you need to make reservations for Academia and Ufizzi in addition, and in advance?
No. It acts as a skip-the-line ticket whenever you want to use it (within the life of the card.)
Just be sure to do the math before purchasing the card: you need to be able to visit quite a number of museums - and use public transport often enough - to break even. Add up the entry fees for the museums you wish to see, and realistically have TIME to see, and compare that to the price of the pass. The only lines you really have to worry about are at the Uffizi and Accademia, and tickets/reservations for just these two can be pre-purchased from this website (English tab at bottom of page):
http://www.b-ticket.com/b-ticket/uffizi/default.aspx
Note that tickets to the Accademia are currently more expensive than usual due to a special exhibit so add that into your estimate. Same with any others who may have temporarily increased prices.
Etdetten,
You may want to read this informative article to help you decide if the Firenze Card is worth it for you: http://www.visitflorence.com/florence-museums/is-firenze-card-worth-it.html
When my mom & I were there, we did not buy it, because we figured it was not worth the cost.
Cost of the card went up last year. Unless all you want to do is see all the museums, it's probably not worth the cost.
You can buy your tickets in advance for the Academia, and the Ufizzi with a skip the line priority, just print out the email and bring with you to show and exchange for a ticket.
http://selectitaly.com/browse/things-to-do/museums?museumCityId=16