The short version: This movie blew chunks.
The animation was great but lacked variation, the music was quite mediochre but the worst part is the story & the characters. The story is the same old, boring "teenager saves earth from alien invasion" in its purest form - utterly uninspiring. The characters are utterly cliché with the exception of totally lacking any realism. Their actions and behaviour is so utterly unrealistic and out of place that you really just want to fast-forward parts of the movie.
Do not get lured by the pretty graphics - as a story this one is a waste of time.