Actually, I thought the Fannings did fairly well, particularly Elle. She had the right "little sister" spirit from the start. As for Dakota, there were a couple of moments where she didn't always hit the mark, but they were few. It's not the equivalent of the FOX dub, but like Castle, Disney's redub of Totoro is both underrated and controversial.
As for Howl, I had no major problem with the voices.
I think hardcore fans of Ghibi's films would bash any attempt to dub their work either way, because I've seen most of them do that to every attempt. Personally, I think it's a sad way to be a fan. I find it no fun at all to dislike something just because it has famous actors in it.
-Jon T.