I have nothing against her personally (how could I, I don't know her!) nor do I hate everything she wears, but I am frustrated by how often she chooses things that just plain don't suit her. Soft, pretty, girly designs rarely flatter her and her posture betrays the fact that, well, she knows it. She often looks uncomfortable in these clothes.
However, when she wears sharper, more structured clothing, with a darker, mod or androgynous styling, she can look fantastic - and she stands straighter, with her shoulders back and her chin up. Since she was going to the Oscars to present, not as a nominee or date, I would have loved to see her wearing a women's tuxedo. That, in my opinion, would have been awesome.
As for her hair - I suspect that when she leaves the hairstylist's chair, it looks great. But she evidently has a habit of running her hands through it, especially when she's nervous, and I think that the moment she steps out on the red carpet, if it isn't pinned up or held back, she just unintentionally ravages the styling.