Tales from Earthsea is sort of like a progressive rock album. On a technical level, it is quite extraordinary. The way the shots and action are arranged are top-notch. Unfortunately, it falls very, very short in terms of its content.
Mind you, I only compare this to progressive rock, because I've been listening to a lot of it lately.
The film starts off with a promising plot. But about 30 minutes in, it doesn't feel like much has changed since then. The beginning shows two dragons fighting in the sky, and this is witnessed by a ship crew below. It is established that seeing a dragon is normal, but to see them fighting viciously is very unusual. The two dragons are never explained again. We are meant to assume that this is a symbol of unbalance in Earthsea's environment.
The story moves very slowly. Its almost like a J.R.R. Tolkein story, fully of allegories surrounded by mythical and medieval occurences. But it takes a long time to reach the point of something, and you are never certain why you are reaching that point. Like Tolkein, it exists within a world of its own, with its own history and mythology. That much is explained, but it is never really explained how the main characters are connected to that.
The characters are never fully explained. My attention was mostly focused on the character of Arren, who is introduced murdering his father, and then running away, having periodic moments of suicidal tendency. This fascinated me, but wasn't touched upon later in the story. It seemed more like Arren was recovering from something, but we never find out what. Its possible his problems may be an allegory for bipolar disorder.
The character of Therru is kept a mystery throughout much of the story. We learn that she was an abused child, and her low social status makes her a severe outcast. But at the end of the movie, she is shown to be immortal, which is never fully explained. It seems like there wasn't enough time to fully round her out as a character.
The antagonist, Cob, is a very confusing character for me. On a simpler note, he's a wizard wishing to gain immortality, but the story alludes to a past he has, which is connected to Earthsea's mythology. The latter isn't explained very much.
Goro Miyazaki definitely has the technical prowess down. For a first time director, he helmed a nicely organized visual treat. But as a storyteller, he needs a ton of work there. And this seems to be the general consensus of the whole thing. Goro Miyazaki, the son of animation icon Hayao Miyazaki, needs to really concentrate on what he wants to say in a story, and how to fully explain that to the audience. It seems like he didn't spend very much adapting the screenplay (based on books by Ursula K. Le Guin), and more time structuring the technical challenges of the movie.
Something nice about Tales from Earthsea: it fits nicely with Studio Ghibli's other films. Its not the best thing they've done, but it doesn't ruin their track record.