If you're thinking about traveling to Italy and renting a car, here's a tip: don't. Take buses and trains. They're cheaper and they involve less yelling. You might even ride for free.
We traveled on public transport about a dozen times and were asked to show valid tickets maybe twice. The payment process on most trains is pretty simple: you buy your tickets, stamp them on the platform, then be ready to show them to a conductor on board. (The stamping machine prints the date and time on the ticket so the conductor can see if you're trying to reuse an old ticket.) We started on the Leonardo Express, a non-stop train from Leonardo da Vinci Airport to Rome's Termini station. Our tickets cost €11 each and nobody ever asked to see them. We used our transit passes on buses in Rome, where there are stamping machines on board but where drivers don't collect fares or inspect tickets; nobody checked those passes at all. Rome's subway systems required valid passes to pass through automated turnstiles, but there was nobody watching for fare-jumpers. On two medium-distance train routes in Tuscany, we dutifully bought and stamped tickets to go from Prato to Florence and from Prato to Lucca. Nobody looked at those tickets either. By that time my dad was a little upset at having spent over €100 on tickets nobody had bothered to inspect.
Venice takes an interesting approach to tickets on its water buses, called vaporetti. ACTV, the public agency which operates the vaporetti, has a nifty radio-tag system for tickets. You buy a ticket and touch it against a special sensor before boarding. There are also ACTV employees on every boat to help dock and undock at stations, but they don't actively check tickets. They do sell tickets. "If you board without a ticket," starts an encouraging note on the ACTV web site, "you must request one from the marinaio (sailor/attendant) at the board platform and before boarding." Translation: you can pay the normal fare of €6.50 by asking the attendant first, but if he asks you for a ticket and you don't have one, you have to pay a fine. We were asked to show our tickets on a single vaporetto but without a physical stamp the attendant would have had to scan our cards electronically to see if they were valid. He just looked at them and walked away.
Fittingly, the very last transport we took in Italy was the most stringent on tickets. Alilaguna, a private company, runs frequent water shuttles from places in Venice to Marco Polo International Airport. As we sailed towards the airport, imagine our shock as a conductor took our printed, stamped, €12 per person tickets and actually punched holes in them! Leave it to a private company to properly check that it's getting fares from its passengers.
Compare this to the roads. We rented an Opel Zafira, a diesel-powered "compact MPV" that snugly fit us all and our luggage. Adam used his laptop with a USB GPS receiver to navigate us out of Rome. There is no single highway that runs through Rome; modern maps show a patchwork of tunnels, boulevards, and bypasses that connect the inner core to the modern ring road and eventually to the A1 autostrada (highway) that runs as far south as Naples and as far north as Milan, over half the length of the Italian peninsula. Once on the autostrada it's pretty smooth: the roads are in great shape, signage is pretty good, and there are rest stops everywhere. The speed limit is 130 km/hr (about 85 mph) and is enforced about as strictly as are transit fares. We paid for this convenience in two ways: many of the autostrade we took were tolled at rates higher than the turnpikes we're used to in New York and Pennsylvania, and gasoline is extraordinarily expensive. You want to complain about $4 a gallon? Try €1.50 for a liter of diesel, or about $9 for a gallon. Our little Zafira cost about €64, or about $100, to fill from 1/4 of a tank. With tolls and the rental car cost, it would have been much less expensive to go from point A to point B on a train (though we couldn't detour to points C and D, as we did en route to Prato).
Once off the autostrade, the real fun begins. Roundabouts are everywhere. Adam's GPS software can offer directions like "take the 2nd exit," but there's little time for judgment about whether the parking lot counts as the "first exit" out of a roundabout. My dad usually likes to complain about too few road signs when he's in an unfamiliar American city. Italy is the opposite way: there are literally dozens of arrow-laden signs after exiting any highway, erected by governments, hotels, shops, historic districts, and in some rare cases, vandals! We thought we were free to ignore these signs with the GPS to guide us, but our hotel in Prato was only accessible by slavishly following the road signs. We ended up illegally parking about a half mile away (my dad guessed, correctly, that the cops wouldn't care) and having Gianni, a worker at the hotel, guide my dad to the right parking lot. Gianni suggested that we get around Tuscany using the trains. We did so happily.
Incidentally, if you need to return a rental car in Venice, don't go to the garage next to the big lighted rental car company signs. Go to the tiny barely-marked garage across the street. Trust me.