Rome's got a great public transportation system. No matter where you want to go, you can get there by train, bus, or tram, or if you're really desperate, taxi. It's all rather cheap (except the taxi) and few Italians ever even pay. No one ever checks.
However, the buses and trams are crowded and smell like body odor, you can't put your feet up on the seats in the train, and taxi drivers will try to rip you off 100% of the time. However, these things are to be expected and are not of major consequence. They will not ruin your day or make it impossible to go about your daily business, quite the opposite in fact when they are saving you miles of walking on cobbled stones.
However, one day I encountered an incident with public transportation that had no precedent. As some friends and I were taking a bus from Villa Borghese (a large park in the center of Rome), the driver stopped the bus, put on his helmet, and took off on his vespa. My friends and I gaped at each other. We gaped at the other passengers and they gaped at us. No one knew what was happening. We waited. Perhaps he ran out to get a beer, or maybe a bite to eat. He'll come back.
We didn't really want to get off the bus because it was a long walk back home and we didn't know when another bus was coming. But it soon became apparent that the bus driver was not coming back. Perhaps he had simply had enough and we had just witnessed an oppressed man shrug a hateful occupation. Either way, we ended up walking miles of cobbledstones to get home. I hope that bus driver is out there somewhere fullfilling his dreams and that our aching feet were worth it.