I have been interested in seeing Whisper of the Heart every since I saw it's sequel -- The Cat Returns -- a few months ago. I'm not sure why Disney decided to release the "sequel" on DVD prior the "original" but it's just as well since you don't have to see one in order to understand what is going on in the other.
In Whisper, an imaginitive girl named Shizuku Tsukishima is trying to find her place in life. In the process she ends up writing a book about a magical cat called The Baron -- a character that she based on a statuette she saw in an antique shop. The Cat Returns movie takes the character of the Baron and develops him into his own story. So while Whisper is about real people doing relatively plausible things, Cat Returns is more of a fantasy tale.
Of the two movies, I liked Whisper better because even though it was set in the "real world" it always felt as thought at it would transition into the realm of fantasy at any moment. There were subtle hints throughout the movie that suggest a magical element, like the fact that the cat named "Moon" (a real one this time) was riding on the train and seemed to be leading Tsukishima somewhere; or the subtle shift in lighting of the Baron statue's eyes which gave the impression that it was alive. Maintaining that balance of imagination and reality was what really makes this movie stand out.
The animation in Whisper was on par with Ghibli's typical high-quality work. It was simple, subtle and enjoyable to watch. The one thing that seperates Ghibli animation from other studios is Ghibli's attention to detail in their portrayal of the character's actions. There are little habits that a character will do that most anyone can recognize and relate to. Like when Tsukishima is stressed out over writing her story, you see her knee bopping up in down in a kind of nervous habit. It's subtle but unexpected, and it's the kind of thing that creates an instant connection between the viewer and the movie.
The music compliments the movie well. Part of Tsukishima's story involves her attempt to translate the song "Take Me Home, Courntry Roads" into Japanese, so that song gets plenty of playtime. It's a good song and was an effective way to interconnect different scenes.
Overall, I thought the movie was great. The conclusion of the story was not especially climactic but was definitely satisfying as the characters acknowledge their feelings for one another.
I would suggest this for kids and adults alike -- and I don't mean that in the Disney-sense where it just means that safe for both kids and adults. This is a movie that is mature enough for adults to genuinely relate to and empathise with, while still displaying a sense of wonder that kids can relate to and enjoy as well.