Upside Down: an interesting concept does not a good film make. While the idea allows for some mesmerizing visuals (even thought the way colors are dealt with almost put those to waste), there is little else that works here. The love story, which should be the core of the film, is poor and unengaging (as well as metaphorically unrelated to the original concept); the writing further shows its limitations by telling rather than showing at least one crucial piece of information. Acting in general, despite the capable cast, is terrible; furthermore, the voice-over is pretentious and irrelevant.
(The same general idea was put to better use in the recent animated short, Head Over Heels.)