I think the biggest thing I have with film-Hermione is her confidence. She's too self assured. Too together and way way way too girl-power (to use Emma's own words). I don't have any issues with Emma's looks because it's really only from Harry's POV that has described Hermione as average or less attractive. Yes, she has buck teeth and bushy hair but maybe that was a Harry thing and not so much a Hermione in general thing.
But what I haven't seen in the movies is the insecure Hermione who uses her booksmarts to compensate for her insecurity about Ron and her social skills. We see Ron's insecurity everywhere in the films. At times almost too much. It's a given that Rupert does comedy so well the film-makers take full advantage of that. To a fault. It a shame that it isn't as evenly balanced with these two. In GOF I fear that we're going to get a good dose of immature/insecure/jealous Ron and not enough jealous/insecure Hermione. Once again we'll get the POV that the boy is the only one at fault here and Hermione comes off as squeeky clean as always.
JKR modelled Hermione after herself as a teenager so I hope the film-makers put back Hermione's weaknesses into GOF.
So yeah, I agree that Hermione's character needs to be scaled back a bit and hopefully with the addition of Luna, Ginny and Neville to the group, the dynamic will be improved.
I'm pleased that Luna's is being cast for OotP. It was her character that really showcased how different the girls were from each other. JKR labeled her the anti-Hermione and boy is she ever. Hopefully seeing these two work off one another will highlight more of Hermione's insecurities and faults as they really are as much as I adore her, she's not perfect.