I just completed half of this trip today. Rome, Dublin, Boston with the balance being in June of this year from the US back to Rome.

A few data points I wanted to pass along. I was unable to do online check-in. I tried multiple times, w/o success. I was a transit passenger into Rome and was unable to get my boarding pass till I got to the gate. There were probably about 40 people like me that needed to get boarding passes and it was quite a mess at the gate. As they needed to input address, phone number, passport details manually which btw I had already done online previously.

The flight from Rome to Dublin was an A321 Neo with life flat. I had secured one of the throne seats but upon printing my boarding pass at the gate, I got moved to the very last row 34 c. The gate agent told me to ask the flight attendants who tried very hard to accommodate my correct seat but alas, I was stuck at the back of the bus. The crew was great though, and provided me with a complementary meal and drink, which was very much appreciated.

in any case, a pleasant ride to Dublin, and then onwards, I did have my throne seat, which was a very nice way to fly across the Atlantic on a narrow body.