Perche

A taxi in Rome is simple. You don't have to worry about whether or not a driver will be there with a sign waiting for you as you exit because if your flight is late a limo service driver may wait a certain amount of time, and then will usually just leave the airport. Don't expect a driver to still be there waiting for you patiently while you are on a three hour flight delay if you have not been able to call and advise them ahead of time.

The only exception might be a limo service arranged by your hotel where they are depending on the hotel to send them repeat business, and you pay them a premium fee.

As said by lost*in*cyberspace, unlike in most USA cities, roman taxis have a set fee so they have no incentive to drive you around. Just take a taxi from an official stand at the airport. They can't add to the 48E fee, except for adding any nominal night fee. Roman cabs tend to be much newer than the cabs in most major U.S. cities so they are usually very comfortable and clean.

It is not typical to tip in Italy. Maybe a few euros in a restaurant if the service was great. In a cab, tipping is much more unheard of than at a restaurant. If you get a good ride give 50E and say keep the change, and the driver will be very appreciative of that. It's not being cheap, things are just structured differently e.g., a living wage, health care insurance, etc, without relying on tips.