Here is Bergman at the peak of his powers creating a richly witty, dark comedy, filled with striking, beautifully played scenes, some tension (will the devil win? in Bergman's universe there is no foregone conclusion), and a good deal of wisdom about the human condition -- withal, an engaging, satisfying story, delivered in a brisk 87 minutes.
Bergman was a great artist; this is not one of his great works; it is a minor but delightful one. But minor work or not, watching the assured writing, cinematography and acting, you know you are in the hands of a master.