Well shot and well edited, as expected from any Edgar Wright film, but the script is highly flawed.
It starts off quite strongly. The cast is great and the first doppelganger-nightclub-dancing scene is fantastic; definitely the high-point of the film. Unfortunately, it's all pretty much downhill from there.
It becomes fairly repetitive and tiresome in the middle, and culminates in an over-the-top and nonsensical ending.