Can't get past the age difference
I love Fred, but he just strikes me as a creepy old man throughout this movie. He basically stalks Joan Leslie at the beginning, showing up at her work (cornering her in a darkrooom!) and her boarding house. And she's 17 and looks it to me, while he is showing every bit of his 44 years.
Their dances together are good, but I cringe when they get romantic.