Pretty much a perfect movie and an old favorite. The cast is excellent. Hepburn is magnificent. My only complaint is that Gregory Peck seems a bit too well put together to play a b-level reporter, but he sells his character's actions and feelings later on very well. Wyler's direction is just right. Auric's score fits in perfectly. Trumbo's script is magnificent. Hilarious, tender, engaging, witty.
There's some weight to things, too. It's not just that the Princess chooses her duty and country over her feelings, and in the process becomes her own person (the character development is exquisite). Trumbo throws in some socioeconomic subtext. The very everyman named Joe Bradley is stuck via his economic circumstances in Rome. But he's also a sucker for the old world charms of the city and falls for a royal. But Princess Anne is trapped by this old world system that serves to keep her from true happiness. She is trapped by monarchism even though she thinks she is making a decision on her own. She has matured, but only so much as the system she was born into allows it. And, although Joe has softened and become more respectable as a person, monarchism is also keeping him from true happiness, and his hard nosed boss now has him so that he won't be economically able to leave Rome and fulfill his possible potential. He's not much better off at the end in some respects. Very adroit writing.
Classic all around.