Although I think Chloe Moretz will be great as the title character, I think it would be interesting (and more realistic) to have Carrie appear the way King described her in the novel. She was not a skinny, attractiveness-hidden teenage girl. She was, according to King's description, "a frog" with some "baby fat" and acne. While Sissy Spacek in the '76 cinematic version (for which she was nominated as best actress), and Angela Bettis in the made-for-TV 2002 (and more loyal to the novel adaption) version did incredible work, they weren't exactly the Carrie from the novel. In the book, she worked on her appearance and overcame her bit-of-a-chubby, acned, persecuted teen to become what Tommy Ross called "beautiful."
The same with Margaret White. Again, while Piper Laurie (who got a best-supporting actress nomination) in the '76 version, and Patricia Clarkson in the '02 version also were incredible in their portrayals, they were not the woman King described. She was a muscular, semi-obese woman with pinned-up hair and rimless glasses that cut into the pudginess of her face.
It would be interesting to see the characters portrayed as such.
Gerard