that picture's very unclear, I can't really form an opinion if she's good. and as for the hair looking crap, I don't think that picture's taken just before filming, she'll probably have someone fix her hair before shooting. and about the age thing, at least she's only appr 10 years older, I mean alan rickman is over 25 years too old

 

Yes but Rickman can ACT! It remains to be seen if she can. I hate book!Snape, but actually watched the horrid movies to see Rickman as Snape. That was the only redeeming value in filmGoF...