It's just as bad when you get off the cruise at Civitavecchia. Plus, when we returned there were other boats disembarking at the same time. It was complete pandemonium. After waiting for almost an hour for our shuttle, we decided to cough up the $230 to get a taxi to drive to the airport so we wouldn't lose our flight.
Plus, it's a good idea to find out in advance, which part of the Rome airport is where your airline is located. They'll drop you off at one spot, you walk in and find out that you're supposed to take a shuttle to the right terminal. In our case, we had to take that shuttle to check with our carrier in the RIGHT terminal, then had to be shuttled back to ANOTHER terminal which had the right gate. Give yourself extra time for this runaround.