Do the Harry Potter characters from the movie look the way you imagine they would, from the books?

I watched the movies before I read the books, so the appearances were kind of imprinted in my mind as I read the books and I never really got a chance to imagine what certain characters looked like for myself, but to people that read the books before seeing the films, did the characters look anything the way you imagined? Do you approve or disapprove of any actors/actresses getting certain parts? I'm particularly curious about your thoughts on Snape and Lupin's actors, but please, talk about whomever else you want.