LOL-I had heard that Venice was smelly and old and full of tourists so I was worried it was going to be NoLA of Europe. When we went it was lovely and I can't wait to return. That said, it was December and I can understand how it would be crowded and stinky in the summer.
Having been to Italy in July and December, no way would I return in summer. Winter or spring? Definitely.
I loved Florence too but Rome, meh. I could never return to Rome and be fine, which is sad because I thought I'd love it.
I loved Florence for the art (David is truly awe inspiring and the Uffizi is so huge and overwhelming but full of amazing things), shopping (gloves and jackets and boots oh my!), and it's walkable and charming. Oh, and the food, too, of course.