As an alternative to Pisa and Florence, the Luca tour is great. The Pisa thing is a waste of time IMHO. Take the picuture and walk 30 minutes back to the bus.
If you have never been to Florence, then I would do that all by itself.
SS Norway (12 times) '85 - '97; Radiance OS 06/01; Island Princess 11/04, Grand Princess 11/04/05, Golden Princess 7/21/06, Golden Princess 2/24/07, Explorer of the Seas 12/23/07, Island Princess 11/15/08