I watched this a couple nights ago. It's pretty charming, in the same vein as Wall-E (though admittedly not as well made). The style used is superb, however. It's truly inviting. Even when catastrophe strikes, the style makes you worry less...if that makes sense.
Though I watched it with horribly made subtitles (everyone are worry), the story is charming enough. It's a mix between the Little Mermaid and Majora's Mask; odd sure, but interesting.
If you liked anything else to come out of Studio Ghibli such as Princess Mononoke or Spirited Away, then you'll probably like this (although, I think the other two are better).