It's a little ghetto but it's very easy to use since it only goes in 2 directions.
Yeah - completely around the city though... best transportation in Rome is your two feet. In terms of public transportation, Rome is far behind, understandably - and the bus systems are WAY confusing - took me living there to figure it all out - I've heard some people's experiences visiting Rome were ruined because of transportation lacking. The Metro in Paris is like any other subway, with transfers and such - very easy to use though, and I only visited it.