The opinions of film critics and veteran writers who attended previews are split down the middle. Here's a sample of some of the harsher ones:
"Compared to his last three films that addressed environmental destruction, morality and pacifism head-on, its themes of love and keeping promises are important but overly minimal."
"Although it's set in the sea there's no sense of scale, and there's not much in the way of uplift either."
"Kids who are used to greater stimulation will probably go for the "Pokemon" movie that opens on the same day instead."
In fact, even Miyazaki himself has admitted that "the reaction from kids at preview screenings was absolutely non-existent, and he's down in the dumps because he tried making something for kids but failed to hit the target."
Ghibli expert and film writer Abo Yukiko takes an affirmative stance.
"Those who want to argue over content should go and watch one of his other films. 'Ponyo' is almost a film to be savored in its entirety rather than picking over it in your head. Ponyo's subtle movements are delightful, and it illustrates Miyazaki's powers of human observation."
I'm sure if Miyazaki had taken his customary polemic approach with this one, certain media would be having a go at him for his 'inveterate left-wing didacticism' or something along those lines instead. It's also instructive that publications who allow the holders of critical opinions to remain anonymous (or more accurately just make shit up) are often the same ones who love to go off on editorial campaigns against internet bulletin boards because they offer their users the exact same courtesy. Me, I'll wait until the crowds die down a bit before going to see the film, but surely it can't be as disappointing as "Howl's Moving Castle".