My wife and I saw this in the theater yesterday. We felt that it was excellent. It tells the story of the experiences of average soldiers rather than telling the overall story of WW I. We appreciated the fact that there were no historians or "talking heads"; the only voices that you hear are from interviews of the soldiers themselves. They used lip-readers to determine some of what was being said by the soldiers in the films, then used actors to voice those words, but primarily it is the recollections of individuals involved.
After the film, there was a "behind the scenes" documentary regarding the process used to make the film. They described the difficulty of choosing what to include, or more accurately what to exclude, from the available footage and voice recordings. They started with hundreds of hours of material, but focused on those on the front, rather than the air corps, navy, etc. I'd love to see more, but I appreciated being able to see what we could.
I highly recommend this film.
CC Griff