Yeah, a fast incubation does ruin things quite a bit. But you don't have to make it a fast incubation and fast zombies. But it does look like they are doing both from what little we have seen, ruining the book.
If that on set footage is any judge, then they are going with the *instantaneous* incubation a la 28 Days Later
. That completely undermines allot of the basic premises for the whole book and makes it more and more likely that this will be just another (excuse the pun) mindless zombie movie, with a Roland Emmerich style disaster movie slant.