If I hadn't read the manga I probably would be giving it straight 10s. Probably.
The movie cuts out enough of the side character's personalities that you don't really wonder too much about their backstories that were also cut out.
Everything actually story-related for the two main characters is pretty much in there, and absolutely gorgeous.
10's for art and sound but story and characters get a 6, impacting my enjoyment and overall score down to an 8.
So, I'd definitely have to say either watch this one before reading the critically-acclaimed manga, or pick the manga over the film. It's hard for me to say this as a die-hard KyoAni fan, but KyoAni, you really could have done better on this one.