Robert Duvall and a general observation
I'd read the book recently and, before watching the movie had heard Robert Duvall was in it. I immediately thought of him as the veteran. Having Mike (sorry, old Neighbour's reference - to some of us he'll always be Mike, just as Andrew Lincoln will always be Egg) as the veteran was a different take on the redemptive figure at the end of the film. Not wrong, or out of place, but not what I was expecting.
Also, as an aside, I thought the scene where apparent cannibals capture a mother and daughter (I think it was) was a little obvious. The not-used scene of the book of a baby being cooked was more subtle but effective.