I can't add much to what has already been said, but it's very disappointing to hear about all the changes from the book. It could still be a very enjoyable movie, but it's a shame that it's possibly not going to be much more than a shell of the novel that inspired it.
I understand that the format of the novel demanded changes and omissions to fit a movie format like all adaptations, and I was fine with creating a roaming protagonist at the center of many of the events, but giving in to the urge to use 28 Days Later
-type fast zombies with rapid transformation says that they had no faith in the idea that they could make wave upon wave of relentless slow zombies frightening. That's kind of bothersome to me since it shows a lack of imagination (and it wouldn't take much, since the book laid everything out for you) and a need to mimic other recent zombie films.
Fast zombies with fast transformation changes the whole dynamic of the story. No one would let them on a plane or through a checkpoint to spread the virus. They might be able to take over individual regions, but as soon as you come upon a natural geographical barrier like a mountain range or ocean that's as far as they'll spread. I'm hoping at least they include an long incubation period in the initial infection stage and then it mutates into something worse to justify the rapid transformations.
I'm also worried that the one article I read about needing an exceptionally long road in Glascow (which is standing in for Philadelphia in the film) doesn't mean that they're going to substitute Philadelphia for the Battle of Yonkers. Why else would you need an extremely long road except to show a tracking shot of the hopelessly large number of zombies heading your way? It could be just long shots of random zombie violence like what was shown in the YouTube videos, though, I guess. It just won't be the same without the Battle of Yonkers, at least, so I hope that makes it.
Anyway, I'm not going to write off the movie, since Pitt seems dedicated to the project and he usually makes pretty good choices, and even with my misgivings on the changes it can still be a very fun movie. I just don't know if it's going to be World War Z