This film really impressed me. Perhaps because it's the only Miyazaki film I've seen which is squarely aimed at adults - but there has to be more to it than that.
Porco Rosso differs from all the earlier Miyazaki-written Ghibli films in that it doesn't have a fantasy setting - it's very specifically set around 1929-30, in Italy and in the islands between Italy and Yugoslavia. Miyazaki's love of aviation and Italy shows through in his usual loving attention to detail - not just the design of the planes, but in historical detail: hyperinflation and the rise of fascism. There are other fantastic little touches, too. My favourite is where the women are rebuidling the plane and you see a shot of Porco sitting smoking a cigarette and rocking a baby's cradle while he waits. I don't know who else would have thought of something like that.
Porco used to be a human, but has turned into a pig, because of a 'spell'. Who put this spell on him? It's one of numerous things we never find out, though we can make some pretty safe assumptions about. Whatever the case, the flashback scene where Porco explains what triggered the transformation is one of the most sublimely beautiful and touching sequences I've ever seen in an animated movie.
In looks, it's nothing at all like his earlier epics, though rather like 'Kiki' in its bright, sparkling, mediterranean backdrops. It has comedy. Unsurprisngly, it has lots of flying action sequences. There is a love story, a beautiful between-the-wars vision of a paradise about to be snatched away, and a mysterious theme about a man who has turned into a pig ("I'm not a person", he tells a bank teller who asks him for a donation 'for the people' (i.e. the Fascist Party)
To me this is a really unique movie. If it reminds me of anything, it's 'Casablanca'. Kids and teenagers may not like it. Personally I think it's better than 'Nausicaa', 'Castle in the Sky' or 'Kiki's Delivery Service' (though the latter comes fairly close.) I like the narrower focus. His epics were just a little impersonal for my tastes.
This film very nearly scored four stars from me.
And yes... having seen 'Tailspin' now, I have to agree wtih Inkwolf. The similarities are too obvious to be coincidence - though I suppose it's concievable that being a feature film, Porco Rosso was actually concieved first (it came out between 1 and 2 years later). On the surface though you have to suspect Miyazaki of lifting some ideas here. It's only Disney's track record of this that's making me wonder was really thought up first.
(NB: this review refers to the subtitled version. I have no idea what the English voice cast is like.)