Originally Posted by You
If you'd really like to see both Pisa & Florence in a day, and money's not an issue, the easiest way to do it would be by taking one of the private tours as AF1 suggested above. It would maximize your time, that's for sure.
I don't agree. The interiors of both the Duomo (Cathedral) and its Baptistry (actually a separate building) in Pisa (the "leaning tower" is actually the Cathedral's bell tower) have very interesting art and architecture that are well worth taking time to see.
Also, I think that you can now climb the leaning tower again.