In fact, I liked the teenagerhood stuff more than I liked the plot. One of the criticisms I remember hearing about the book is that Harry mopes around for so many chapters not doing anything. Which is understandably ennoying when you are reading, and he's still moping as much in chapter 7 as in chapter 3. But in the movie, Harry's moping is so real, so 14-year-old-ish, so completely believable, that it is rather touching. It's a great setting for exploring teenage behavior (rather like Buffy: the Vampire Slayer). I've always felt that the twins, for instance, were massively underused. In this movie, even more so than the last, you get to watch teenagers, including the twins, act like teenagers. Harry and Ron's "I'm sorry" conversation is quintessential male adolescence: it gives you shivers of nostalgia--for about two seconds until you remember that you would rather be dead than live through the teenage years again.
One of the things that is somewhat different from the book is Harry's utter reluctance to participant in the championship (if I remember correctly, he had mixed feelings in the book). It still raises the question of what on earth do these insane adults think they are doing exposing these kids to so much danger? But the movie raises the issue of adult culpability to the level of metaphor. The movie is really, in a way, about growing up--your friends change, you change, hormones enter the picture, emotions get overwrought, you find yourself in situations where you are shorter, less clever and more vulnerable than everyone else. The end scene (which I won't relate) gives Harry a positively heroic maturity.
And kudos to Daniel Radcliffe who evinces a quality of raw emotion that was missing in the other films. One gets the feeling that Harry is just tired--tired of the fights, tired of Voldemort, sick and tired of protecting people. It also emphasizes that Harry's gift--the reason we bother to read about him at all--is not his intelligence or even his broomstick riding. He isn't particularly chivalrous or honorable. He's just decent. Mostly decent. He's everyguy.
The movie, by the way, is exceedingly dark. I agree with my brother Eugene (see www.eugenewoodbury.blogspot.com) that Rowlings' emphasis on being "real" by killing people off in each book means she has to keep raising the stakes so that a bigger, scarier, yuckier death has to happen in every book. (This is not, by the way, particularly good writing: C.J. Cherryh never has to resort to it.) One of my other siblings once suggested that Goblet of Fire should have been the first book, rather than the book everything was leading up to. That being said, if the movie Goblet of Fire is taken by itself, rather than as one more saga in the "oh-is-it-dark-enough-yet?" Harry Potter plotline, the horror works. (Although, again, it is NOT for little kiddies.) The filming is not as atmospheric as in the last, but the movie does move a great deal quicker than the first two (and has the merit of feeling like a movie rather than like a filmstrip as the first one did).
All in all I recommend it.