Back in 2005, when Howl's Moving Castle came out, I remember that while there were some highly positive reviews of the film, the general reaction seemed to mostly be that the film was, by some margin, the least successful work to date by Hayao Miyazaki. The reaction seemed to range from "Worth watching, but his least good film" to "Miyazaki's only dud". It took me several years to finally get around to watching the movie, and I must admit that I'm not sure why so many people were down on it, except by virtue of comparison to the films in Miyazaki's oeuvre before it.
My guess is that Miyazaki's previous work had been so good as to simply make a subsequent film that wasn't as good look even worse than it is by comparison, and that I was able to avoid looking at Howl's through Spirited Away-colored glasses by virtue of having waited so long to finally watch the movie. (I'd forgotten I owned it on DVD, believe it or not.) Miyazaki's two previous movies, Princess Mononoke and Spirited Away, are truly great films that manage to rise above being "classics of genre" and become actual "classics". So a more pedestrian effort like Howl's is standing in a much larger shadow. But I would say that the films need to be judged for what they are, and not what the other films around them imply they should be; and that a continuum exists that must be acknowledged. Surely there is a greater range of possibilities for a Miyazaki film than "Classic" on one end, and "Dud" on the other. I mean, not every James Bond film is Casino Royale or On Her Majesty's Secret Service, but that doesn't mean that every film not at that end of the pool is therefore Live and Let Die.
So, as for Howl's specifically, I found it highly enjoyable, if occasionally maddening in its Miyazakian way of not explaining stuff.
I'd like to flesh this out a bit, but I've only watched the film once and I don't remember a lot of the specifics. I recall some highly typical Miyazaki visual flair; what often makes his films so astounding is his ability to not just think up lots of weird stuff but to also come up with ways to depict that weird stuff in a world that looks familiar to us and yet still not have all of his weird stuff look ridiculously out-of-place. The "Moving Castle" itself is a piece of work, an enormous, ramshackle steam-powered vehicle that putt-putts around the countryside and maybe even from one world to another. It's an amazing piece of design.
I don't recall a whole lot of the story, although I do remember that I found it by turns captivating and a little frustrating, because Miyazaki didn't really explain nearly as much as I would have liked. Miyazaki has always been of the "let the viewer figure some stuff out" camp of filmmakers, but in Howl's, I found myself thinking -- for the first time ever in a Miyazaki film -- along the lines of, "Geez, a little more exposition might not be the worst idea here."
Characters? I liked and sympathized with them all, especially the Prince who is losing his soul as war engulfs his land. The most memorable character, though, is the inanimate scarecrow who has only one facial expression and who can't make any gestures at all, and yet somehow, through Miyazaki's genius, is able to seem like a totally autonomous actor in the story.
So yes, I liked Howl's Moving Castle, quite a bit. Is it Miyazaki's least successful film, story-wise? Maybe. But if it doesn't quite clear the bar, it at least gets up there, which a lot of films never do.