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!