I saw this film when I was a nuerotic teen, and it spoke to me then and still does. It shows Sinatra and Day to be great together, and Mr. S was still really serious about his acting, unlike later when he lost interest.
The movie reflects its time, showing the Sinatra character as the outsider/rebel, through a slight messing of his hair (toupe) and a loosened tie, reflecting the still uptight society. It took so little to define an outcast.
The music is great although the song he keeps trying to write is not as good as it should have been given the buildup. The title song, Young At Heart, is a better one, although it does not seem to fit the story which heads down a forlorn path until the happy ending saves it. Sinatra shows the inner sadness and self-destructive nature of those of us who are self-involved and neurotic. Funny too is how the only goal for Sinatra's character is to write a hit tune; nothing else will do.
Doris is absolutely adorable and so desirable that you almost feel she is too good for Frank, although Gig Young plays such a likeable, charming jerk that you do eventually get why she might like the more interesting Sinatra.
The three sisters are a hoot, (although they appear too old to be living at home with Dad) all seeking marriage as their only hope in this world, and competing with each other very subtley while trying to love one another; very 50's.
And what more can we say about one of the great Barrymore's, Ethyl. She is so good and on target without going for the obvious choices. Certainly she deserved a better role at this time of her career, but no bitterness shows through. She is a pro. Not sure where this fell in terms of her eventual demise, but she looks quite aged here, so it may have been among her last films. Obviously, I love this film.