Catherine Deneuve and her real life older sister Françoise Dorléac are radiant. Danielle Darrieux plays mom to the sisters (and does a great job too). Gene Kelly is miscast, but he obviously wanted to be in a film with the sisters, so who could blame him. The visuals are all sixties (in the best sense of that).
George Chakaris, who played Riff in West Side Story on the West End London stage and Bernardo in the West Side Story film, does a solid job. A guy from Ohio, with a Greek background, plays an Irish and Puerto Rican street thug, and a French guy (and it looked like he was signing and delivering his lines in French).
Bonus: For a Friday Night Movie, here's The Umbrellas of Cherbourg: