The movie works mainly thanks to it's concept: A world with split gravity. Despite my expectations that this would become old quite fast they actually made a good use of it throughout the movie. The problem is that it's just not something exceptional (Yasuhiro Yoshiura's previous work "Time of Eve" is that). The plot should have been more about the world than Patema and Age or just less cliché. It was also hard to buy into the totalitarian regime and the villain was unrefined and frankly dumb. I make it sound a lot worse once again but it isn't a bad movie by any means.

For those who are wondering: this and the movie Upside Down (with Kirsten Dunst) have no connection to each other. It's a mere coincidence (and a four-part webseries which covers the beginning of this movie was released before the trailers for the latter).
Also, the "over-funded" Kickstarter for the UK + a few EU countries release is still going for another 16 days - https://www.kickstarter.com/projects/alltheanime/patema-inverted-ultimate-edition.