The other comments I have read all seem accurate to me (except I don't think Maguerite is necessarily an aristocrat, but the poor protege of one). The innocent nudity, the gorgeous photography and glamorous Roman locations, the capturing of a moment of social freedom in the sixties, are all superb. Although the director has a reputation for making exploitation films, at least in the year 2000 it doesn't seem to me that this film qualifies as one, since the nudity, sex and drugs are relatively tame, and the film now reads as a serious dramatic effort, at least to me.
What I found fascinating about the film was the portrayal of the progress of the emotional relationship of Armand and Marguerite- it covers how they met, love won and lost several times, their emotional conflicts and life choices as a result of their feelings for each other. In this it seems to me highly realistic, perceptive and insightful. It captures the emotional life of the very wealthy, young and beautiful elite- joy, confusion, hedonism, love and also despair.
It follows the evolution of the relationship in such detail that, at times, I found the film dragging a bit, but this was a minor problem for me compared to the joy of seeing such a deep exploration of their relationship. Instead of the single roller-coaster ride of snipped-down Hollywood fare, we enter fully into another world by dwelling there through several different plot climaxes.