This is a wonderful, fun and touching movie. At a screening at Sundance 2007 the director described it as a musical, and it really is. The primary actors are musicians and their songs tie the movie together and tie you to them. Although the primary cast aren't actors as a first profession, they are very natural together and the film flows very well because of it. Everyone involved in this film has a great passion for music, and it is very infectious. It is one of the few films I have seen in 7 years at Sundance that received a standing ovation.
From the Sundance film guide: "A Dublin busker, who ekes out a living playing guitar and repairing vacuum cleaners for his dad's shop, meets a young Czech immigrant who sells roses on the same street. She likes his song, and what's more she has a broken vacuum cleaner! They soon find themselves playing music together in a nearby music store (since she can't afford a piano, the owner lets her play his floor models). Over the course of a week, they form a musical rapport and, newly inspired, decide to record an album.
Once may loosely be classified as a musical, but it has a refreshing vérité inflection. Conceived by director John Carney as a "video album," it sports a scrappy, unembellished naturalism. Carney took a risk in choosing professional musicians over professional actors, but Glen Hansard (of the well-known Irish band the Frames) and Marketa Irglova (a Czech singer/songwriter) are not only remarkably charming together but they're equally adept with the more melancholy shades (Hansard's lonely soul, stuck on an old flame; Irglova struggling to support a mother and daughter). Burdened and brokenhearted, their musical bond is the heart of the film and of their love.
Great music aside, what makes this film special is how little effort it seems to exert. If it's possible to be blindsided by simplicity--a light touch, Once does it." John Nein