This film probably would've been charming anyway, but what particularly makes it is the turns put in by its leads - Amy Adams is delicious and Frances McDormand just right, and their interplay hits all the right notes. As the somewhat grave older love interest, Ciaran Hinds (previously known to me as Julius Caesar in Rome) is good, too, and another of my Brit female actor crushes stakes, Shirley Henderson, also cut a swathe, her character pleasingly sharp-edged and aloof, always black and incessantly smoking, of course. (Such wonderful names, by the way, too! Guinevere Pettigrew, Delysia Lafosse, Edyth Dubarry, and so on...)
It's frothy, but has a serious side as well; without particularly being a 'message' film, it's not blind to the social realities of the milieu it depicts (that of the well-to-do and the rather less so at the very tail end of the jazz age), and when the happy ending we knew all along was coming does, indeed come, it's unsurprising but doesn't rankle in the slightest. The film - it is what it is, and entertaining at it.
(w/ Kai)