score:4
Taxis in Rome are more expensives than in other European capitals. For example, a short travel (10 minutes) in the city center cost us 10 euros. As you said, the airports have fixed fees.
Taxis are white and have a license number in both sides and inside. Also, obviouslly, they have the word "taxi". It's very important that you never take a taxi from someone that offer you to get you to the city, because be sure that this is not an official taxi (a real taxi driver will never do that).
Also, it is convenient that you ask the driver about the price before hop on the taxi.
Anyway, be careful also with the official taxis. I've heard histories about scams even from this kind of taxis. If you have any problem, take the taxi license and the car plate number.