how is that drive?
Depends on what you are doing. If only getting from MXP to Florence...take the train, you do not want a car in Florence. If you need a car after Florence, rent outside Florence.
have a lease car for two months ..picking it up at MXP
The drive is all on a 4 to 8 lane freeway. About 4 hour drive. Traffic likely at the Milan's Tangenziale (Beltway). Boring flat plain like Illinois from Milan to Bologna, then the A1 goes through major mountain range between Bologna and Prato/Calenzano (near Florence). The portion through the mountains is heavily trafficked also by many trucks and there are numerous tunnels in this portion. Curves are minimal and soft (Italians like straight freeways even through mountains, they just tunnel through them) But be careful, especially with the truck drivers as they don't even bother to signal when they want to pass, they just cut in front of you without warning.