My first watchthrough, I watched with subtitles. I don't watch too much anime but I usually watch normal shows with subtitles anyway just because I prefer knowing exactly what the dialogue is. After watching it again with the english dub, I now realise how much of the film went completely over my head from first viewing. If you haven't watched it, please do! It's a really enjoyable film!
My only criticism would be the music in the first half of the film, I would much rather personally if it was just instrumental. Except from that, fantastic!