When we went to Italy in May 2001 we flew into Rome (arrived early, around 8am) and took the train to Florence the same day. It was an easy trip and we still arrived in Florence around 3pm - would've been earlier except that we had to wait a couple hrs in Rome for a piece of luggage. :-( Sure, we were tired when we arrived in Florence, but I'd rather spend my jet lag recovery time in Florence than Rome. (We spent 5 days in Rome on the way home.) At any rate, arriving in Rome and going on to Florence the same day is very do-able and we didn't find it overly taxing.

On the other hand, if you're just visiting Florence and not on a really tight schedule, it should be workable to fly there directly.

Cindy in Harrisonburg, VA