Favorite places to visit and cycle in central/northern Italy?

[bluebug32]

Any specific shop recommendations for renting more high-end road bikes? I know Florence by Bike has a nice rental fleet.

Also, would you guys recommend spending the entire time in Florence and taking day trips or splitting the time by staying in Siena or Bologna (or other surrounding place) for a couple of nights? Is there enough to do there?

[Crankin]

I only saw Bologna from the train, so I can't comment. But, it did look nice.
I would spend at least a night in Siena. It's a college town, so in addition to the duomo, the piazza, the museums, etc. there's quite a "vibe." The shopping and food, well, just as good as Florence. Florence, while I really enjoyed spending a few days there, is huge. I wouldn't ride my bike in that traffic! I wouldn't ride in the walled city of Siena, either, but it's easy to get outside the walls.
The shop we rented from did not have high end bikes; they were crappy mountain bikes. However, that might have changed, since this was in 2004.