[Effendi]

In Milan and Rome all operators have 3G HSPA coverage, as in any city in Italy. So coverage is not an issue.

Wind's Internet No Stop offer is good and you pay 9 euro/month, not a cent more. If you use more than 1GB/month your speed is limited to 32kbps. It's hard to use more than 1GB on a phone without tethering, so it shouldn't be a problem to you.

NovercaGiga is not an option by TIM, it's a virtual operator and hard to find for non-Italians. The same applies to COOP Voce.

Both TIM and Vodafone have offers for smartphones called TIMxSmartphone and Mobile Internet. They have some limitations (no tethering, no voip...) but they are fine to be used on a smartphone/iphone.

TIM, Vodafone and 3 have shops at Fiumicino airport, Wind doesn't. But all three seem to be inside the gates area, so quite unuseful when you arrive. But there's a fourth shop at the arrivals, called "Smartphone", at Terminal 3. They could have prepaid cards of all the operators. BTW you can find phone shops in the centre without any problem. I know there's a shopping centre close to the airport where surely Wind has a shop (you can find Wind shops nearly in any shopping centre in Italy).