Just finished watching this (the THORA release), and honestly I was slightly disappointed. It's a really great film, but I don't think it quite manages to match the quality of Makoto Shinkai's previous works. The ending felt a bit disappointing imo; it just left me with far to many questions.
It didn't even properly explain how they got back out of that hole, let alone anything else.
As for the art... despite the far more fantastical and imaginitive setting, it all just felt a bit plain compared to the exquisite detail of his other films. It was much closer in style to a Ghibli film than a Shinkai film (which imo is a step backwards; others might not agree).
The soundtrack was superb, though. Lovely music, and the effects and voice acting were spot on too.
All that said, it is still a masterpiece. While it might not be as amazing as 5cm per Second and The Place Promised In Our Early Days (and that's not really much of a criticism), it is still far better than most other anime films I've seen. Definitely a must watch; especially if you're a Ghibli fan, since their films were clearly a big influence.