If you wish to check out other alternatives, here's a quick guide from this blog:
TIM: the PAYG SIM card costs €10, which includes €5 of credit towards calls and data. The option “TIM PER SMARTPHONE” costs €2 a week for up to 250 MB of data. To activate it if you already have a TIM SIM, just text TIMSMART ON to 40916. This way avoids any “activation” charges that a shop might try to foist on you. It stays activated, automatically debiting your PAYG balance, until you deactivate it by calling TIM customer services on 119.Vodafone: as with TIM, the PAYG SIM card costs €10, which includes €5 of credit. The data option “Mobile Internet” costs €3 per week for 250 MB… but the first week is free. You do the math. As with TIM, it renews automatically until you disconnect or run out of credit.Wind: like TIM and Vodafone, a “SIM ricaricabile” costs €10, with €5 credit included. Wind’s “Internet No Stop Daily” option costs nothing to activate, and debits your PAYG credit €1 on every day that you connect to the Web. There’s a fair use limit, of 50 MB, and you pay nothing if you don’t use the Web on any day. Alternatively, “Internet No Stop” costs €5 to activate (free until September 4th, 2011) plus €9 for a month of traffic up to 1 GB.3: Known as “Tre” in Italy, 3 charges more for SIM cards, so it only really makes sense for longer stays and/or heavy users. A 3 PAYG SIM card costs €30, which breaks down as €7 for the SIM and €23 credit preloaded on it. Thirty days of data, with a 3 GB limit and a daily ceiling of 100 MB, costs just €5. Note that, in my experience, you’re more likely to have connection problems with 3 in rural areas. Cities should be fine, but if you’re lodging in the sticks, ask locally about network reception.
Other useful links: