AmericanInAStrangeLand The service provided is nearly the same for every operator as they all use the same physical infrastructure owned by Telecom Italia (not everywhere, but in your case it is). To be honest, the only real differences are the technical support and the latency to overseas servers (you may be interested if you play online games, for example). For example, if you want a good and fast technical support you shouldn't sign a contract, for example, with Fastweb as their call center operators are known to be not trained enough.
If you allow me, I'd recommend Tiscali with the assistance of @andreagdipaolo: cheap and reliable. Understand and be understood in case of problems is a big difficult for a non Italian speaker as you are (but trust me, also for us )