All,
Just got back from 10-days in Italy (5 in Florence and 5 in Roma). The trip was great, our small group of 5 embraced lots of the suggestions from Rick and this topic board. We went with all carry-on luggage on our trip to Italy, and then checked luggage on our way home.
Florence:
While in Florence we visited the Duomo, David ( in the Galleria dell'Accademia), Cinque Terre and a Farm to Table trip to Tuscany (along with doing the leather market). The weather was very pleasant with rain only on one evening. Recommendations - book in advance for tours because the lines get long. Also, go exploring early in the day.
Roma:
Vatican City with an early entry into the Sistine Chapel and Colosseum Tours were great - again, book early so you don't stand in long lines and wait for hours to get in. Visit all the churches you can, each seem to be more grand than the other. Impressive artwork on the walls and ceilings. Check out the Mose di Michelangelo at the Basilica di San Pietro in Vincoli - you can also see the Chains of St. Peter. Check out the outdoor markets in Roma like Campo de Fiori (but remember, you cannot transport Pork sausage back to the USA in your luggage - I found out the hard way). Before going to Campo de Fiori, visit the Piazza Navona. Must see's are also the Trevi Fountain (watch out for pick-pockets and street peddlers) and Spanish Steps.
When we arrived at Leonardo da Vinci-Fiumicino Airport, the train was down between the airport and Termini train station, we were all routed to buses for the trip - be patient - you are in Italy!
All in all the trip was very enjoyable and we would go back.
Have fun on your trip to Italy!