Definitely a must watch anime, especially when you're looking for sci-fi movies, but it lacks character introduction. The concept of living in a world that can be called real and not real, it's so fantastic and unique. Probably the best Sci-fi concept I've watched. The Animation is just right even tho it's a 3D animation trying to be in anime style, it kinda feels right when you get halfway the movie. The delivery of the concept is so great that you would not mind questioning how much of it is fantasy.
The one thing I think that is lacking is character introduction and development. I kinda wished there are more Ichigyou-Katakagi moments, tho I may be biased because i like slice of life(or so they call it) more than sci-fi.
If you're looking for sci-fi, this is definitely a must watch. And if you're looking for romance, it's good, but there definitely are better ones.