I also liked that deviation from the book.Welcome Kaleb, I didn't see you post before!
I agree with PoTW, while it was different than it was in the book to have Eustace remain in dragon form for a lot of the film, I rather liked what they did with it -- it gave him a more important role to play and added excitement without taking away from the theme of redemption.
The transformation itself kind of disappointed me, for it is nothing at all like I imagined it, but I see why the change was necessary.